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Search query: "hinode"
represents closeness of match. The more the better ! Max 5.

Chromospheric Jet and Growing ''Loop'' Observed by Hinode: New Evidence of Fan-Spine Magnetic Topology Resulting From Flux Emergence      

Wei Liu   Submitted: 2010-12-08 11:25

We present observations of a chromospheric jet and growing ''loop'' system that show new evidence of a fan-spine topology resulting from magnetic flux emergence. This event, occurring in an equatorial coronal hole on 2007 February 9, was observed by the Hinode Solar Optical Telescope in the Ca II H line in unprecedented detail. The predecessor of the jet is a bundle of fine material threads that extend above the chromosphere and appear to rotate about the bundle axis at ~50 km/s (period <200 s). These rotations or transverse oscillations propagate upward at velocities up to 786 km/s. The bundle first slowly and then rapidly swings up, with the transition occurring at the onset of an A4.9 flare. A loop expands simultaneously in these two phases (velocity: 16-135 km/s). Near the peak of ... [READ MORE]

Authors: Liu, Wei; Berger, Thomas E.; Title, Alan M.; Tarbell, Theodore D; and Low, B. C.
Projects: Hinode/SOT

Publication Status: Accepted by ApJ, 2010 Dec 8; movie available at http://www.lmsal.com/~weiliu/public/hinode/2007-02-09_sot-jet (360 MB)
Last Modified: 2010-12-10 10:16
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Chromospheric evaporation flows and density changes deduced from Hinode/EIS during an M1.6 flare      

Peter Gomory   Submitted: 2016-02-16 13:12

We analyzed high-cadence sit-and-stare observations acquired with the Hinode/EIS spectrometer and HXR measurements acquired with RHESSI during an M-class flare. During the flare impulsive phase, we observe no significant flows in the cooler Fe XIII line but strong upflows, up to 80-150 km/s, in the hotter Fe XVI line. The largest Doppler shifts observed in the Fe XVI line were co-temporal with the sharp intensity peak. The electron density obtained from a Fe XIII line pair ratio exhibited fast increase (within two minutes) from the pre-flare level of 5.01x10^(9) cm^(-3) to 3.16x10^(10) cm^(-3) during the flare peak. The nonthermal energy flux density deposited from the coronal acceleration site to the lower atmospheric layers during the flare peak was found to be 1.34x10^(10) erg/s/cm^(2) ... [READ MORE]

Authors: Gomory, P.; Veronig, A. M.; Su, Y.; Temmer, M.; Thalmann, J. K.
Projects: Hinode/EIS

Publication Status: Accepted for publication in Astronomy and Astrophysics
Last Modified: 0000-00-00 00:00
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HINODE OBSERVATIONS OF COHERENT LATERAL MOTION OF PENUMBRAL FILAMENTS DURING A X-CLASS FLARE      

Sanjay Gosain   Submitted: 2009-11-04 03:08

The X-3.4 class flare of 13 December 2006 was observed with a high cadence of 2 minutes at 0.2 arc-sec resolution by HINODE/SOT FG instrument. The flare ribbons could be seen in G-band images also. A careful analysis of these observations after proper registration of images show flare related changes in penumbral filaments of the associated sunspot, for the first time. The observations of sunspot deformation, decay of penumbral area and changes in magnetic flux during large flares have been reported earlier in the literature. In this Letter, we report lateral motion of the penumbral filaments in a sheared region of the -sunspot during the X-class flare. Such shifts have not been seen earlier. The lateral motion occurs in two phases, (i) motion before the flare ribbons move across ... [READ MORE]

Authors: S. Gosain, P. Venkatakrishnan and Sanjiv Kumar Tiwari
Projects: Hinode/SOT

Publication Status: Accepted in ApJ Letters
Last Modified: 2009-11-04 08:42
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The Relationship Between Solar Coronal X-Ray Brightness and Active Region Magnetic Fields: A Study Using High-Resolution Hinode Observations      

Soumitra Hazra   Submitted: 2015-03-02 05:03

By using high-resolution observations of nearly co-temporal and co-spatial Solar Optical Telescope spectropolarimeter and X-Ray Telescope coronal X-ray data onboard Hinode, we revisit the problematic relationship between global magnetic quantities and coronal X-ray brightness. Co-aligned vector magnetogram and X-ray data were used for this study. The total X-ray brightness over active regions is well correlated with integrated magnetic quantities such as the total unsigned magnetic flux, the total unsigned vertical current, and the area-integrated square of the vertical and horizontal magnetic fields. On accounting for the inter-dependence of the magnetic quantities, we inferred that the total magnetic flux is the primary determinant of the observed integrated X-ray brightness. Our ... [READ MORE]

Authors: Soumitra Hazra, Dibyendu Nandy, B Ravindra
Projects: Hinode/SOT,Hinode/XRT

Publication Status: 2015, Solar Physics, 290, 771
Last Modified: 2015-03-02 09:52
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Calibration of Hinode/XRT for Coalignment      

keiji yoshimura   Submitted: 2015-07-07 23:20

We present coalignment calibration procedures for the X-ray Telescope (XRT) onboard the Hinode satellite in this paper. We performed not only an XRT stand-alone calibration, but also cross-calibration using data from the Helioseismic and Magnetic Imager (HMI) and the Atmospheric Imaging Assembly (AIA) onboard the Solar Dynamics Observatory (SDO). Several new methods described herein may also be useful for the coalignment calibration of other instruments. We have developed a database of coalignment coefficients and software to access it, so that all XRT images can be easily and accurately overlaid onto the images from other instruments, especially AIA and HMI.

Authors: Yoshimura, K., McKenzie, David E.
Projects: Hinode/XRT,SDO-AIA,SDO-HMI

Publication Status: Solar Physics, accepted
Last Modified: 2015-07-08 12:55
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Benchmarking atomic data for astrophysics: Fe VII and other cool lines observed by Hinode EIS      

Giulio Del Zanna   Submitted: 2009-11-20 15:50

The EUV spectrum of Fe VII is reviewed, using new rates for electron impact excitation, atomic structure calculations, and experimental data. In particular, solar observations of a Sunspot loop spectrum obtained from the Hinode EUV Imaging Spectrometer (EIS) are used. Previous line identifications, mostly based on laboratory data, have been assessed. Large discrepancies between observed and predicted line intensities and wavelengths are found for the decays from the 3s2 3p5 3d3 configuration, which are strong EUV lines. We ascribe these discrepancies to incorrect line identifications. A number of new identifications are proposed. With these, very good agreement between theory and experimental data is found. A few transitions, in particular from the 3s2 3p6 3d 4s ... [READ MORE]

Authors: Del Zanna, G.
Projects: Hinode/EIS

Publication Status: A&A in press
Last Modified: 2009-11-23 13:51
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A revised radiometric calibration for the Hinode/EIS instrument      

Giulio Del Zanna   Submitted: 2013-05-09 04:26

An assessment of the in-flight radiometric calibration of the Hinode EUV Imaging Spectrometer (EIS) is presented. This is done with the line ratio technique applied to a wide range of observations of the quiet Sun, active regions and flares from 2006 until 2012. The best diagnostic lines and the relevant atomic data are discussed in detail. Radiances over the quiet Sun are also considered, with comparisons with previous measurements. Some departures in the shapes of the ground calibration responsivities are found at the start of the mission. These shapes do not change significantly over time, with the exception of the shorter wavelengths of the EIS short-wavelength (SW) channel, which shows some degradation. The sensitivity of the SW channel at longer wavelengths does not ... [READ MORE]

Authors: G. Del Zanna
Projects: Hinode/EIS

Publication Status: accepted for publication in A&A
Last Modified: 2013-05-09 09:48
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Emission Height and Temperature Distribution of White-Light Emission Observed by Hinode/SOT from the 2012 January 27 X-class Solar Flare      

Kyoko Watanabe   Submitted: 2013-10-08 07:42

White-light emissions were observed from an X1.7 class solar flare on 2012 January 27, using three continuum bands (red, green, and blue) of the Solar Optical Telescope on board the Hinode satellite. This event occurred near the solar limb, and so differences in the locations of the various emissions are consistent with differences in heights above the photosphere of the various emission sources. Under this interpretation, our observations are consistent with the white-light emissions occurring at the lowest levels of where the Ca II H emission occurs. Moreover, the centers of the source regions of the red, green, and blue wavelengths of the white-light emissions are significantly displaced from each other, suggesting that those respective emissions are emanating from progressively lower ... [READ MORE]

Authors: Kyoko Watanabe, Toshifumi Shimizu, Satoshi Masuda, Kiyoshi Ichimoto, and Masanori Ohno
Projects: Hinode/SOT

Publication Status: Published in ApJ, 776, 123 (2013)
Last Modified: 2013-10-09 12:17
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Study of White-Light Flares Observed by Hinode      

Haimin Wang   Submitted: 2008-12-03 07:39

White-light flares are considered as the most energetic flaring events that are observable in optical broad-band continuum of solar spectrum. They have not been commonly observed. Observations of white-light flares with sub-arcsecond resolution have been very rare. The continuous high resolution observations of Hinode provide an unique opportunity to systematically study the white-light flares with a spatial resolution around 0.2 arcsec. We surveyed all the flares above GOES magnitude C5.0 since the launch of Hinode in 2006 October, 13 of them were covered by Hinode G-band observations. We analyzed the peak contrast and equivalent area (calculated via integrated excess emission contrast) of these flares as a function of GOES X-ray flux, and found that the cut-off visibility ... [READ MORE]

Authors: Haimin Wang
Projects: Hinode/SOT

Publication Status: Research in Astronomy and Astrophysics, 2009, in press
Last Modified: 2008-12-03 13:24
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Evolution of twist-shear and dip-shear during X-class flare of 13 December 2006: Hinode observations      

Sanjay Gosain   Submitted: 2010-07-15 04:34

The non-potentiality (NP) of the solar magnetic fields is measured tradi- tionally in terms of magnetic shear angle i.e., the angle between observed and potential field azimuth. Here, we introduce another measure of shear that has not been studied earlier in solar active regions, i.e. the one that is associated with the inclination angle of the magnetic field. This form of shear, which we call as the ?dip-shear?, can be calculated by taking the difference between the observed and potential field inclination. In this Letter, we study the evolution of dip-shear as well as the conventional twist-shear in a -sunspot using high- resolution vector magnetograms from Hinode space mission. We monitor these shears in a penumbral region located close to flare site during 12 and 13 ... [READ MORE]

Authors: Sanjay Gosain and P. Venkatakrishnan
Projects: Hinode/SOT

Publication Status: Accepted for publication in ApJ Letters
Last Modified: 2010-07-15 07:47
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Observations of Sunspot Oscillations in G band and Ca II H line with Solar Optical Telescope on Hinode      

Kaori Nagashima   Submitted: 2007-09-07 09:11

Exploiting high-resolution observations made by the Solar Optical Telescope onboard Hinode, we investigate the spatial distribution of power spectral density of oscillatory signal in and around NOAA active region 10935. The G-band data show that in the umbra the oscillatory power is suppressed in all frequency ranges. On the other hand, in Ca II H intensity maps oscillations in the umbra, so-called umbral flashes, are clearly seen with the power peaking around 5.5 mHz. The Ca II H power distribution shows the enhanced elements with the spatial scale of the umbral flashes over most of the umbra but there is a region with suppressed power at the center of the umbra. The origin and property of this node-like feature remain unexplained.

Authors: Kaori Nagashima, Takashi Sekii, Alexander G. Kosovichev, Hiromoto Shibahashi, Saku Tsuneta, Kiyoshi Ichimoto, Yukio Katsukawa, Bruce W. Lites, Shin'ichi Nagata, Toshifumi Shimizu, Richard A. Shine, Yoshinori Suematsu, Theodore D. Tarbell, and Alan M. Title
Projects: Hinode

Publication Status: Accepted for publication in PASJ (Hinode Special Issue), astro-ph/0709.0569
Last Modified: 2007-09-07 09:11
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Microflare Heating of a Solar Active Region Observed with NuSTAR, Hinode/XRT, and SDO/AIA      

Paul Wright   Submitted: 2017-07-21 08:11

NuSTAR is a highly sensitive focusing hard X-ray (HXR) telescope and has observed several small microflares in its initial solar pointings. In this paper, we present the first joint observation of a microflare with NuSTAR and Hinode/XRT on 2015 April 29 at ~11:29 UT. This microflare shows heating of material to several million Kelvin, observed in Soft X-rays (SXRs) with Hinode/XRT, and was faintly visible in Extreme Ultraviolet (EUV) with SDO/AIA. For three of the four NuSTAR observations of this region (pre-, decay, and post phases) the spectrum is well fitted by a single thermal model of 3.2-3.5 MK, but the spectrum during the impulsive phase shows additional emission up to 10 MK, emission equivalent to A0.1 GOES class. We recover the differential emission measure (DEM) using SDO/AIA, ... [READ MORE]

Authors: Paul J. Wright, Iain G. Hannah, Brian W. Grefenstette, Lindsay Glesener, S?m Krucker, Hugh S. Hudson, David M. Smith, Andrew J. Marsh, Stephen M. White, Matej Kuhar
Projects: GOES X-rays,Hinode/XRT,NuSTAR,SDO-AIA

Publication Status: ApJ (accepted)
Last Modified: 2017-07-21 21:31
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Response of Hinode XRT to quiet Sun, active region and flare plasma      

Giulio Del Zanna   Submitted: 2014-05-07 02:32

Aims: We examine the response of the Hinode X-Ray Telescope (XRT), using simultaneous observations with the Hinode Extreme-ultraviolet Imaging Spectrometer (EIS), for a flare, an active region and a quiet Sun region. We also examine the relative intensity calibration of EIS and XRT. Methods: EIS differential emission measure distribution (DEM) curves were used to create synthetic spectra with the CHIANTI atomic database. The contribution of spectral lines and continuum emission to each of the XRT channels was determined from the synthetic spectra, which were then convolved with the effective area of each XRT channel. The predicted total count rates for each channel were compared with the observed count rates. The effects of varying elemental abundances and the temperature range for the ... [READ MORE]

Authors: O'Dwyer B., Del Zanna, G. and Mason, H.E.
Projects: Hinode/EIS,Hinode/XRT

Publication Status: printed in A&A, DOI: 10.1051/0004-6361/201016346
Last Modified: 2014-05-07 06:01
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An Intriguing Chromospheric Jet Observed by Hinode: I. Fine Structure Kinematics and Evidence of Unwinding Twists      

Wei Liu   Submitted: 2009-10-28 08:18

We report a chromospheric jet lasting for more than 1 hr observed by Hinode Solar Optical Telescope in unprecedented detail. The ejection occurred in three episodes separated by 12-14 min, with the amount and velocity of material decreasing with time. The upward velocities range from 438 to 33 km/s, while the downward velocities of the material falling back have smaller values (mean: -56 km/s) and a narrower distribution (standard deviation: 14 km/s). The average acceleration inferred from parabolic space-time tracks is 141 m/s^2, a fraction of the solar gravitational acceleration. The jet consists of fine threads (0.5-2.0 arcsec wide), which exhibit coherent, oscillatory transverse motions perpendicular to the jet axis and about a common equilibrium position. These motions propagate ... [READ MORE]

Authors: Wei Liu, Thomas E. Berger, Alan M. Title, Theodore D. Tarbell
Projects: Hinode/SOT

Publication Status: Accepted by ApJ Letters (2009 Oct 27); movies available online at http://sun.stanford.edu/~weiliu/eprints/2009/2009-05_Ca-jet/paper-I_movies
Last Modified: 2009-11-09 10:29
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Hinode X-Ray Telescope Detection of Hot Emission from Quiescent Active Regions: A Nanoflare Signature?      

Joan Schmelz   Submitted: 2009-02-13 14:52

The X-Ray Telescope (XRT) on the Japanese/USA/UK {it Hinode (Solar-B)} spacecraft has detected emission from a quiescent active region core that is consistent with nanoflare heating. The fluxes from 10 broadband X-ray filters and filter combinations were used to constructed Differential Emission Measure (DEM) curves. In addition to the expected active region peak at Log T $=$ 6.3-6.5, we find a high-temperature component with significant emission measure at Log T $>$ 7.0. This emission measure is weak compared to the main peak -- the DEM is down by almost three orders of magnitude -- which accounts of the fact that it has not been observed with earlier instruments. It is also consistent with spectra of quiescent active regions: no Fe XIX lines are observed in a CHIANTI synthetic ... [READ MORE]

Authors: Schmelz, J.T., Saar, S.H., DeLuca, E.E., Golub, L., Kashyap, V.L., Weber, M.A. Klimchuk, J.A.
Projects: Hinode/XRT

Publication Status: Accepted for publication in ApJ Letters
Last Modified: 2009-02-14 10:40
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Velocity vectors of a quiescent prominence observed by Hinode/SOT and the MSDP (Meudon)      

R. Chandra   Submitted: 2009-12-02 06:27

The dynamics of prominence fine structures is a challenge to understand the formation of cool plasma prominence embedded in the hot corona. Recent observations from the high resolution Hinode/SOT telescope allow us to compute velocities perpendicularly to the line-of-sight or transverse velocities. Combining simultaneous observations obtained in H-alpha with Hinode/SOT and the MSDP spectrograph operating in the Meudon solar tower we derive the velocity vectors of a quiescent prominence. The velocities perpendicular to the line-of-sight are measured by time slice technique, the Dopplershifts by the bisector method. The Dopplershifts of bright threads derived from the MSDP reach 15 km/s at the edges of the prominence and are between +/- 5 km/s in the center of the prominence. Even though ... [READ MORE]

Authors: Schmieder, B., Chandra, R., Berlicki, A., Mein, P.
Projects: Hinode/SOT,SoHO-MDI

Publication Status: Submitted in A & A
Last Modified: 2009-12-02 17:20
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Calibrating Data from the Hinode/X-Ray Telescope and Associated Uncertainties      

Adam Kobelski   Submitted: 2013-12-18 02:05

The X-Ray Telescope (XRT) onboard the Hinode satellite, launched 23 September 2006 by the Japanese Aerospace Exploration Agency (JAXA) is a joint mission between Japan, the United States, and the United Kingdom to study the solar corona. In particular XRT was designed to study solar plasmas with temperatures between 1 and 10 MK with ≈1″ pixels (≈2″ resolution). Prior to analysis, the data product from this instrument must be properly calibrated and data values quantified in order to assess accurately the information contained within. We present here the standard methods of calibration for these data. The calibration is performed on an empirical basis which uses the least complicated correction that accurately describes the data while suppressing spurious features. ... [READ MORE]

Authors: Adam R. Kobelski, Steven H. Saar, Mark A. Weber, David E. McKenzie, Katharine K. Reeves
Projects: Hinode/XRT

Publication Status: 26 pages, 16 figures, Accepted for publication in Solar Physics
Last Modified: 2013-12-18 09:50
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Magnetic Structure of Umbral Dots Observed with Hinode Solar Optical Telescope      

Hiroko Watanabe   Submitted: 2008-11-06 20:49

High resolution and seeing-free spectroscopic observation of a decaying sunspot was done with the Solar Optical Telescope aboard Hinode satellite. The target was NOAA 10944 located in the west side of the solar surface from March 2 to March 4, 2007. The umbra included many umbral dots (UDs) with size of ~300 km in continuum light. We report the magnetic structures and Doppler velocity fields around UDs, based on the Milne-Eddington inversion of the two iron absorption lines at 6302 angstrom. The histograms of magnetic field strength(B), inclination angle(i), and Doppler velocity(v) of UDs showed a center-to-limb variation. Observed at disk center, UDs had (1)slightly smaller field strength (Delta B=-17 Gauss) and (2)relative blue shifts (Delta v=28 m s-1) compared to their ... [READ MORE]

Authors: Hiroko Watanabe, Reizaburo Kitai, Kiyoshi Ichimoto, Yukio Katsukawa
Projects: Hinode/SOT

Publication Status: accepted for publication in PASJ Vol.61 No.2, astro-ph/0811.1074
Last Modified: 2008-11-07 11:22
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Propagating slow magnetoacoustic waves in coronal loops observed by Hinode/EIS      

Tongjiang Wang   Submitted: 2009-02-25 16:09

We present the first Hinode/EIS observations of 5 min quasi-periodic oscillations detected in a transition-region line (He II) and five coronal lines (Fe X, Fe XII, Fe XIII, Fe XIV, and Fe XV) at the footpoint of a coronal loop. The oscillations exist throughout the whole observation, characterized by a series of wave packets with nearly constant period, typically persisting for 4-6 cycles with a lifetime of 20-30 min. There is an approximate in-phase relation between Doppler shift and intensity oscillations. This provides evidence for slow magnetoacoustic waves propagating upwards from the transition region into the corona. We find that the oscillations detected in the five coronal lines are highly correlated, and the amplitude decreases with increasing temperature. The amplitude of ... [READ MORE]

Authors: T. J. Wang, L. Ofman, and J. M. Davila
Projects: Hinode/EIS

Publication Status: ApJ, May 2009 - v696 issue, (in press)
Last Modified: 2009-03-11 00:19
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Small Scale Magnetic Flux Emergence Observed with Hinode/Solar Optical Telescope      

Kenichi Otsuji   Submitted: 2007-09-20 06:15

We observed small scale magnetic flux emergence in a sunspot moat region by the Solar Optical Telescope (SOT) aboard the Hinode satellite. We analyzed filtergram images observed in the wavelengths of Fe 6302 angstrom, G-band and Ca II H. In Stokes I images of Fe 6302 angstrom, emerging magnetic flux were recognized as dark lanes. In G-band, they showed their shapes almost the same as in Stokes I images. These magnetic flux appeared as dark filaments in Ca II H images. Stokes V images of Fe 6302 angstrom showed pairs of opposite polarities at footpoints of each filament. These magnetic concentrations are identified to correspond to bright points in G-band/Ca II H images. From the analysis of time-sliced diagrams, we derived following properties of emerging flux, which are consistent with ... [READ MORE]

Authors: Kenichi Otsuji, Kazunari Shibata, Reizaburo Kitai, Satoru Ueno, Shin'ichi Nagata, Takuma Matsumoto, Tahei Nakamura, Hiroko Watanabe, Saku Tsuneta, Yoshinori Suematsu, Kiyoshi Ichimoto, Toshifumi Shimizu, Yukio Katsukawa, Theodore D. Tarbell, Bruce W. Lites, Richard A. Shine, and Alan M. Title
Projects: Hinode/SOT

Publication Status: Accepted for publication in PASJ (Hinode Special Issue), astro-ph/0709.3207
Last Modified: 2010-05-13 09:17
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Active Region Moss: Doppler Shifts from Hinode/EIS Observations      

Durgesh Tripathi   Submitted: 2012-05-02 00:02

Studying the Doppler shifts and the temperature dependence of Doppler shifts in moss regions can help us understand the heating processes in the core of the active regions. In this paper we have used an active region observation recorded by the Extreme-ultraviolet Imaging Spectrometer (EIS) onboard Hinode on 12-Dec-2007 to measure the Doppler shifts in the moss regions. We have distinguished the moss regions from the rest of the active region by defining a low density cut-off as derived by Tripathi et al. (2010). We have carried out a very careful analysis of the EIS wavelength calibration based on the method described in Young et al. (2012). For spectral lines having maximum sensitivity between log T = 5.85 and log T = 6.25 K, we find that the velocity distribution peaks at around 0 km/s ... [READ MORE]

Authors: Durgesh Tripathi, Helen E. Mason, James A. Klimchuk
Projects: Hinode/EIS

Publication Status: Accepted for publication in The Astrophysical Journal
Last Modified: 2012-05-02 11:15
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Hydrodynamic Modeling of Coronal Loops with Hinode and STEREO      

Markus J. Aschwanden   Submitted: 2009-01-08 16:54

The hydrodynamic evolution of impulsively-heated coronal loops and their subsequent cooling can now be modeled with multi-wavelength imaging instruments in soft X-ray (SXR) and extreme ultraviolet (EUV) wavelengths. Using analytical approximations to the hydrodynamic evolution of the density n(s,t) and temperature T(s,t) of an impulsively-heated loop (as a function of the loop length coordinate s and time t) we show an example how lightcurves observed with HINODE/XRT, EIS, GOES, and STEREO/EUVI can be modeled with a forward-fitting method in order to infer the maximum heating rate, the heating duration, and the cooling time of a heated loop during a small B1-class flare on 2007-Feb-01, previously analyzed by Warren et al. (2007).

Authors: Aschwanden M.J.
Projects: Hinode/EIS

Publication Status: Astronomical Society of the Pacific Conference Series, Beyond Discovery - Toward Understanding, Second Hinode Science Meeting, 29 Sept - 3 Oct 2008, Boulder, Colorado, USA, (eds. M.Cheung, B.Lites, T.Magara, J.Mariska, and K.Reeves), Vol ..., (subm., 2009 Jan 8)
Last Modified: 2009-01-09 09:37
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Velocity Characteristics of Evaporated Plasma Using Hinode/EIS      

Ryan Milligan   Submitted: 2009-02-25 09:58

This paper presents a detailed study of chromospheric evaporation using the EUV Imaging Spectrometer (EIS) onboard Hinode in conjunction with HXR observations from RHESSI. The advanced capabilities of EIS were used to measure Doppler shifts in 15 emission lines covering the temperature range T = 0.05-16MK during the impulsive phase of a C-class flare on 2007 December 14. Blueshifts indicative of the evaporated material were observed in six emission lines from Fe XIV-XXIV (2-16 MK). Upflow velocity was found to scale with temperature as v_up (km/s) ≈ 5−17 T (MK). Although the hottest emission lines, Fe XXIII and Fe XXIV, exhibited upflows of >200 km/s, their line profiles were found to be dominated by a stationary component in stark contrast to the predictions of the ... [READ MORE]

Authors: Ryan O. Milligan, Brian R. Dennis
Projects: Hinode/EIS,RHESSI

Publication Status: ApJ (accepted)
Last Modified: 2009-04-29 04:11
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Flare Footpoint Regions and a Surge Observed by the Hinode/EUV Imaging Spectrometer (EIS), RHESSI, and SDO/AIA      

Amir Caspi   Submitted: 2015-10-28 16:05

The Extreme-ultraviolet Imaging Spectrometer (EIS) on the Hinode spacecraft observed flare footpoint regions coincident with a surge for a M3.7 flare observed on 25 September 2011 at N12 E33 in active region 11302. The flare was observed in spectral lines of O VI, Fe X, Fe XII, Fe XIV, Fe XV, Fe XVI, Fe XVII, Fe XXIII and Fe XXIV. The EIS observations were made coincident with hard X-ray bursts observed by the Reuven Ramaty High Energy Solar Spectroscopic Imager (RHESSI). Overlays of the RHESSI images on the EIS raster images at different wavelengths show a spatial coincidence of features in the RHESSI images with the EIS upflow and downflow regions, as well as loop-top or near-loop-top regions. A complex array of phenomena was observed including multiple evaporation regions and the ... [READ MORE]

Authors: George A. Doschek, Harry P. Warren, Brian R. Dennis, Jeffrey W. Reep, Amir Caspi
Projects: Hinode/EIS,RHESSI,SDO-AIA

Publication Status: Published -- Doschek, G. A., Warren, H. P., Dennis, B. R., Reep, J. W., & Caspi, A. 2015, ApJ, 813, 32; DOI 10.1088/0004-637X/813/1/32
Last Modified: 2015-11-02 10:52
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Different Patterns of Chromospheric Evaporation in a Flaring Region Observed with Hinode/EIS      

Ying Li   Submitted: 2010-11-22 18:39

We investigate the chromospheric evaporation in the flare of 2007 January 16 using line profiles observed by the EUV Imaging Spectrometer (EIS) onboard Hinode. Three points at flare ribbons of different magnetic polarities are analyzed in detail. We find that the three points show different patterns of upflows and downflows in the impulsive phase of the flare. The spectral lines at the first point are mostly blue shifted, with the hotter lines showing a dominant blue-shifted component over the stationary one. At the second point, however, only weak upflows are detected; in stead, notable downflows appear at high temperatures (up to 2.5-5.0 MK). The third point is similar to the second one only that it shows evidence of multi-component downflows. While the evaporated plasma falling back ... [READ MORE]

Authors: Y. Li & M. D. Ding
Projects: Hinode/EIS

Publication Status: Accepted for publication in ApJ
Last Modified: 2010-11-22 23:55
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Solar surface emerging flux regions: a comparative study of radiative MHD modeling and Hinode SOT observations      

Mark Cheung   Submitted: 2008-06-23 14:31

We present results from numerical modeling of emerging flux regions on the solar surface. The modeling was carried out by means of 3D radiative MHD simulations of the rise of buoyant magnetic flux tubes through the convection zone and into the photosphere. Due to the strong stratification of the convection zone, the rise results in a lateral expansion of the tube into a magnetic sheet, which acts as a reservoir for small-scale flux emergence events at the scale of granulation. The interaction of the convective downflows and the rising magnetic flux undulates it to form serpentine field lines emerging into the photosphere. Observational characteristics including the pattern of emerging flux regions, the cancellation of surface flux and associated high speed downflows, the convective ... [READ MORE]

Authors: M. C. M. Cheung, M. Schuessler, T.D. Tarbell & A. M. Title
Projects: Hinode/SOT

Publication Status: Accepted for publication in ApJ
Last Modified: 2008-09-23 20:59
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Propagation of a sausage soliton in the solar lower atmosphere observed by Hinode/SOT      

Teimuraz Zaqarashvili   Submitted: 2010-04-19 08:18

Acoustic waves and pulses propagating from the solar photosphere upwards may quickly develop into shocks due to the rapid decrease of atmospheric density. However, if they propagate along a magnetic flux tube, then the non-linear steepening may be balanced by tube dispersion effects. This may result in the formation of a sausage soliton. The aim of this Letter is to report observational evidence of a sausage soliton in the solar chromosphere. A time series of the CaII H line obtained at the solar limb with the Solar Optical Telescope (SOT) on board Hinode is analysed. Observations show an intensity blob, which propagates from 500 to 1700 km above the solar surface with a mean apparent speed of 35 km/s. The speed is much higher than the expected local sound speed, therefore the blob cannot ... [READ MORE]

Authors: Zaqarashvili, T. V., Kukhianidze, V. and Khodachenko, M. L.
Projects: Hinode/SOT

Publication Status: MNRAS (in press)
Last Modified: 2010-04-19 08:23
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On the Force-Freeness of the Photospheric Sunspot Magnetic Fields as Observed from Hinode (SOT/SP)      

Sanjiv Kumar Tiwari   Submitted: 2011-09-22 07:18

A magnetic field is force-free if there is no interaction between it and the plasma in the surrounding atmosphere, i.e., electric currents are aligned with the magnetic field, giving rise to zero Lorentz force. The computation of various magnetic parameters, such as magnetic energy (using the virial theorem), gradient of twist of sunspot magnetic fields (computed from the force-free parameter alpha), and any kind of extrapolation, heavily hinges on the force-free approximation of the photospheric sunspot magnetic fields. Thus, it is of vital importance to inspect the force-free behavior of sunspot magnetic fields. The force-free nature of sunspot magnetic fields has been examined earlier by some researchers, ending with incoherent results. Accurate photospheric vector field measurements ... [READ MORE]

Authors: Sanjiv Kumar Tiwari
Projects: Hinode/SOT

Publication Status: Accepted for publication in the Astrophysical Journal
Last Modified: 2011-09-22 13:03
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Comparison of Hinode/XRT and RHESSI detection of hot plasma in the non-flaring solar corona      

Fabio Reale   Submitted: 2009-09-30 05:07

We compare observations of the non-flaring solar corona made simultaneously with Hinode/XRT and with RHESSI. The analyzed corona is dominated by a single active region on 12 November 2006. The comparison is made on emission measures. We derive emission measure distributions vs temperature of the entire active region from multifilter XRT data. We check the compatibility with the total emission measure values estimated from the flux measured with RHESSI if the emission come from isothermal plasma. We find that RHESSI and XRT data analyses consistently point to the presence of a minor emission measure component peaking at log T ~ 6.8-6.9. The discrepancy between XRT and RHESSI results is within a factor of a few and indicates an acceptable level of cross-consistency.

Authors: F. Reale, J. M. McTiernan, P. Testa
Projects: Hinode/XRT,RHESSI

Publication Status: ApJL, 704, L58
Last Modified: 2009-10-01 07:42
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Magnetic Field Structures in a Facular Region Observed by THEMIS and Hinode      

Yang Guo   Submitted: 2010-03-11 03:44

The main objective of this paper is to build and compare vector magnetic maps obtained by two spectral polarimeters, i.e. THEMIS/MTR and Hinode SOT/SP, using two inversion codes (UNNOFIT and MELANIE) based on the Milne-Eddington solar atmosphere model. To this end, we used observations of a facular region within active region NOAA 10996 on 23 May 2008, and found consistent results concerning the field strength, azimuth and inclination distributions. Because SOT/SP is free from the seeing effect and has better spatial resolution, we were able to resolve small magnetic polarities with sizes of 1'' to 2'', and we could detect strong horizontal magnetic fields, which converge or diverge in negative or positive facular polarities. These findings support models which suggest the existence of ... [READ MORE]

Authors: Guo, Y., Schmieder, B., Bommier, V., Gosain, S.
Projects: Hinode/SOT,THEMIS/MTR

Publication Status: Solar Physics (2010), 262, 35
Last Modified: 2010-03-12 09:44
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Analysis of Flows Inside Quiescent Prominences as Captured by Hinode/Solar Optical Telescope      

Michael Freed   Submitted: 2016-02-09 19:54

Developing an understanding of how magnetic fields can become entangled in a prominence is important for predicting a possible eruption. This work investigates the kinetic energy and vorticity associated with plasma motion residing inside quiescent prominences. These plasma flow characteristics can be utilized to improve our understanding of how the prominence maintains a stable magnetic field configuration. Three different contrast-enhanced solar prominence observations from \textit{Hinode}/Solar Optical Telescope were used to construct velocity maps -- in the plane of the sky -- via a Fourier local correlation tracking program. The resulting velocities were then used to perform the first ever analysis of the two-dimensional kinetic energy and enstrophy spectra of a prominence. Enstrophy ... [READ MORE]

Authors: M. S. Freed, D. E. McKenzie, D. W. Longcope, and M. Wilburn
Projects: Hinode/SOT

Publication Status: Published
Last Modified: 2016-02-10 10:11
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Characteristics that Produce White-Light Enhancements in Solar Flares Observed by Hinode/SOT      

Kyoko Watanabe   Submitted: 2017-10-27 06:12

To understand the conditions that produce white-light (WL) enhancements in solar flares, a statistical analysis of visible continuum data as observed by Hinode/Solar Optical Telescope (SOT) was performed. In this study, approximately 100 flare events from M- and X-class flares were selected. The time period during which the data were recorded spans from January 2011 to February 2016. Of these events, approximately half are classified as white-light flares (WLFs), whereas the remaining events do not show any enhancements of the visible continuum (non-WLF; NWL). In order to determine the existence of WL emission, running difference images of not only the Hinode/SOT WL (G-band, blue, green, and red filter) data but also the Solar Dynamics Observatory/Helioseismic and Magnetic Imager ... [READ MORE]

Authors: Kyoko Watanabe, Jun Kitagawa, Satoshi Masuda
Projects: GOES X-rays,Hinode/SOT,RHESSI,SDO-HMI

Publication Status: accepted for publication in ApJ
Last Modified: 2017-10-27 10:44
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Coronal-Temperature-Diagnostic Capability of the Hinode/X-Ray Telescope Based on Self-Consistent Calibration. II. Calibration with on-Orbit Data      

Noriyuki Narukage   Submitted: 2013-07-18 01:13

The X-Ray Telescope (XRT) onboard the Hinode satellite is an X-ray imager that observes the solar corona with the capability of diagnosing coronal temperatures from less than 1 MK to more than 10 MK. To make full use of this capability, Narukage et al. (Solar Phys. 269, 169, 2011) determined the thickness of each of the X-ray focal-plane analysis filters based on calibration measurements from the ground-based end-to-end test. However, in their paper, the calibration of the thicker filters for observations of active regions and flares, namely the med-Be, med-Al, thick-Al and thick-Be filters, was insufficient due to the insufficient X-ray flux used in the measurements. In this work, we recalibrate those thicker filters using quiescent active region data taken with multiple filters of XRT. ... [READ MORE]

Authors: Noriyuki Narukage, Taro Sakao, Ryouhei Kano, Masumi Shimojo, Amy Winebarger, Mark Weber, Kathy K Reeves
Projects: Hinode/XRT

Publication Status: accepted for publication in Solar Physics
Last Modified: 2013-07-18 18:47
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SPECTROSCOPIC ANALYSIS OF AN EIT WAVE/DIMMING OBSERVED BY HINODE/EIS      

Feng Chen   Submitted: 2010-08-19 21:26

EUV Imaging Telescope (EIT) waves are a wavelike phenomenon propagating outward from the coronal mass ejection source region, with expanding dimmings following behind. We present a spectroscopic study of an EIT wave/dimming event observed by the Hinode/Extreme-ultraviolet Imaging Spectrometer. Although the identification of the wave front is somewhat affected by the pre-existing loop structures, the expanding dimming is well defined. We investigate the line intensity, width, and Doppler velocity for four EUV lines. In addition to the significant blueshift implying plasma outflows in the dimming region as revealed in previous studies, we find that the widths of all four spectral lines increase at the outer edge of the dimmings. We illustrate that this feature can be well explained by the ... [READ MORE]

Authors: F. Chen, M. D. Ding and P. F. Chen
Projects: Hinode/EIS

Publication Status: Published in the ApJ
Last Modified: 2010-08-20 09:50
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Depth-dependent global properties of a sunspot observed by Hinode (SOT/SP)      

Sanjiv Tiwari   Submitted: 2015-08-26 13:32

The three dimensional structure of sunspots has been extensively studied for the last two decades. A recent advancement of the Stokes inversion technique prompts us to revisit the problem. In the present work, we aim to investigate the global depth-dependent thermal, velocity and magnetic properties of a sunspot, as well as the interconnection between various local properties. High quality Stokes profiles of the disk centered, regular, leading sunspot of NOAA AR 10933 acquired by the Solar Optical Telescope/Spectropolarimeter onboard the Hinode spacecraft are analyzed. To obtain the depth-dependent stratification of the physical parameters, we have utilized the recently developed spatially coupled version of the SPINOR inversion code. We first study the azimuthally averaged physical ... [READ MORE]

Authors: Tiwari, Sanjiv K.; van Noort, Michiel; Solanki, Sami K.; Lagg, Andreas
Projects: Hinode/SOT

Publication Status: A&A, accepted
Last Modified: 2015-08-27 10:27
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G-band and Hard X-ray Emissions of the 2006 December 14 flare observed by Hinode/SOT and RHESSI      

Kyoko Watanabe   Submitted: 2010-04-26 19:53

We report on G-band emission observed by the Solar Optical Telescope onboard the Hinode satellite in association with the X1.5-class flare on 2006 December 14. The G-band enhancements originate from the footpoints of flaring coronal magnetic loops, coinciding with non-thermal hard X-ray bremsstrahlung sources observed by the Reuven Ramaty High Energy Solar Spectroscopic Imager. At the available 2 minute cadence, the G-band and hard X-ray intensities are furthermore well correlated in time. Assuming that the G-band enhancements are continuum emission from a blackbody, we derived the total radiative losses of the white-light flare (white-light power). If the G-band enhancements additionally have a contribution from lines, the derived values are overestimates. We compare the white-light ... [READ MORE]

Authors: Kyoko Watanabe, Sam Krucker, Hugh Hudson, Toshifumi Shimizu, Satoshi Masuda, Kiyoshi Ichimoto
Projects: Hinode/SOT,RHESSI

Publication Status: ApJ (in press)
Last Modified: 2010-04-27 07:50
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RAPID ENHANCEMENT OF SHEARED EVERSHED FLOW ALONG THE NEUTRAL LINE ASSOCIATED WITH AN X6.5 FLARE OBSERVED BY HINODE      

Na Deng   Submitted: 2011-05-10 12:41

We present G-band and Ca II H observations of NOAA AR 10930 obtained by Hinode/SOT on 2006 December 6 covering an X6.5 flare. The Local Correlation Tracking technique was applied to the foreshortening-corrected G-band image series to acquire horizontal proper motions in this complex ??? active region. With the continuous high-quality, spatial and temporal resolution G-band data, we not only confirm the rapid decay of outer penumbrae and darkening of the central structure near the flaring neutral line, but also unambiguously detect for the first time the enhancement of the sheared Evershed flow (average horizontal flow speed increased from 330 ± 3.1 to 403 ± 4.6 m s–1) along the neutral line right after the eruptive ... [READ MORE]


Authors: Na Deng, Chang Liu, Debi Prasad Choudhary and Haimin Wang
Projects: Hinode/SOT

Publication Status: Published in ApJL
Last Modified: 2011-05-11 09:12
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Patterns of Flows in an Intermediate Prominence Observed by Hinode      

Kwangsu Ahn   Submitted: 2010-09-16 12:35

The investigation of plasma flows in filaments/prominences gives us clues to understanding their magnetic structures. We studied the patterns of flows in an intermediate prominence observed by Hinode/SOT. By examining a time series of Hα images and Ca II H images, we have found horizontal flows in the spine and vertical flows in the barb. Both of these flows have a characteristic speed of 10-20 km s?1. The horizontal flows displayed counterstreaming. Our detailed investigation revealed that most of the moving fragments in fact reversed direction at the end point of the spine near a footpoint close to the associated active region. These returning flows may be one possible explanation of the well-known counterstreaming flows in prominences. In contrast, we have found vertical ... [READ MORE]

Authors: Ahn, Kwangsu; Chae, Jongchul; Cao, Wenda; Goode, Philip R.
Projects: Hinode/SOT

Publication Status: Published in the ApJ
Last Modified: 2010-09-20 07:38
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Thermal structure of hot non-flaring corona from Hinode/EIS      

Fabio Reale   Submitted: 2014-03-12 08:40

In previous studies a very hot plasma component has been diagnosed in solar active regions through the images in three different narrow-band channels of SDO/AIA. This diagnostic from EUV imaging data has also been supported by the matching morphology of the emission in the hot Ca XVII line, as observed with Hinode/EIS. This evidence is debated because of unknown distribution of the emission measure along the line of sight. Here we investigate in detail the thermal distribution of one of such regions using EUV spectroscopic data. In an active region observed with SDO/AIA, Hinode/EIS and XRT, we select a subregion with a very hot plasma component and another cooler one for comparison. The average spectrum is extracted for both, and 14 intense lines are selected for analysis, that probe the ... [READ MORE]

Authors: A. Petralia, F. Reale, P. Testa, G. Del Zanna
Projects: Hinode/EIS,Hinode/XRT,SDO-AIA

Publication Status: accepted for publication in A&A
Last Modified: 2014-03-12 09:56
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On-Orbit Sensitivity Evolution of the EUV Imaging Spectrometer on Hinode      

John Mariska   Submitted: 2012-11-20 09:27

Since its launch on 22 September 2006, the EUV Imaging Spectrometer onboard the Hinode satellite has exhibited a gradual decay in sensitivity. Using spectroheliograms taken in the Fe VIII 185.21 Angstrom and Si VII 275.35 Angstrom emission lines in quiet regions near Sun center we characterize that decay. For the period from December 2006 to March 2012, the decline in the sensitivity can be characterized as an exponential decay with an average time constant of 7358 ? 1030 days (20.2 ? 2.8 years). Emission lines formed at temperatures >10^6.1 K in the quiet-Sun data exhibit solar-cycle effects.

Authors: J. T. Mariska
Projects: Hinode/EIS

Publication Status: Solar Physics, in press
Last Modified: 2012-11-20 20:24
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Comparison between Hinode/SOT and SDO/HMI, AIA Data for the Study of the Solar Flare Trigger Process      

Yumi Bamba   Submitted: 2014-07-07 11:06

Understanding the mechanism that produces solar flares is important not only from the scientific point of view but also for improving space weather predictability. There are numerous observational and computational studies, which attempted to reveal the onset mechanism of solar flares. However, the underlying mechanism of flare onset remains elusive. To elucidate the flare trigger mechanism, we have analyzed several flare events which were observed by Hinode/Solar Optical Telescope (SOT), in our previous study. Because of the limitation of SOT field of view, however, only four events in the Hinode data sets have been utilizable. Therefore, increasing the number of events is required for evaluating the flare trigger models. We investigated the applicability of data obtained by the ... [READ MORE]

Authors: Yumi Bamba, Kanya Kusano, Shinsuke Imada, Yusuke Iida
Projects: Hinode/SOT,SDO-AIA,SDO-HMI

Publication Status: Accepted to PASJ, Hinode special issue
Last Modified: 2014-07-09 13:41
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Study on Triggering Process of Solar Flares Based on Hinode/SOT Observations      

Yumi Bamba   Submitted: 2013-09-21 06:19

We investigated four major solar flare events that occurred in active regions NOAA 10930 (December 13 and 14, 2006) and NOAA 11158 (February 13 and 15, 2011) by using data observed by the Solar Optical Telescope (SOT) onboard the Hinode satellite. To reveal the trigger mechanism of solar flares, we analyzed the spatio-temporal correlation between the detailed magnetic field structure and the emission image of the Ca H line at the central part of flaring regions for several hours prior to the onset of flares. We observed in all the flare events that the magnetic shear angle in the flaring regions exceeded 70 degrees, as well as that characteristic magnetic disturbances developed at the centers of flaring regions in the pre-flare phase. These magnetic disturbances can be classified into two ... [READ MORE]

Authors: Y. Bamba, K. Kusano, T. T. Yamamoto, and T. J. Okamoto
Projects: Hinode/SOT

Publication Status: in press.
Last Modified: 2013-09-30 10:01
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Anatomy of a solar flare: Part I. The solar quake measurements of the December 14, 2006 X-class flare with GONG, Hinode and RHE      

Sarah Matthews   Submitted: 2010-05-28 01:23

Some of the most challenging observations to explain in the context of existing flare models are those related to the lower atmosphere and below the solar surface. Such observations, including changes in the photospheric magnetic field and seismic emission, indicate the poorly understood connections between energy release in the corona and its impact in the photosphere and the solar interior. Using data from Hinode, TRACE, RHESSI and GONG we study the temporal and spatial evolution of the 14 December 2006 X-class flare in the chromosphere, photosphere and the solar interior. We report for the first time the detection of a solar quake using time-distance methods applied to GONG data. We then investigate the connections between the emission at various atmospheric depths, with ... [READ MORE]

Authors: Sarah Matthews, Sergei Zharkov, Valentina Zharkova
Projects: Hinode/SOT

Publication Status: ApJ (submitted)
Last Modified: 2010-05-28 03:01
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Space-Time Distribution of G-Band and Ca II H-Line Intensity Oscillations in Hinode/SOT-FG Observations      

John Lawrence   Submitted: 2009-07-29 22:25

We study the space-time distributions of intensity fluctuations in 2 ? 3 hour sequences of multi-spectral, high-resolution, high-cadence broad-band filtergram images (BFI) made by the SOT-FG system aboard the Hinode spacecraft. In the frequency range 5.5 < f < 8.0 mHz both G-band and Ca II H-line oscillations are suppressed in the presence of magnetic fields, but the suppression disappears for f > 10 mHz. By looking at G-band frequencies above 10 mHz we find that the oscillatory power, both at these frequencies and at lower frequencies too, lies in a mesh pattern with cell scale 2 ? 3 Mm, clearly larger than normal granulation, and with correlation times on the order of hours. The mesh pattern lies in the dark lanes between stable cells found in time-integrated G-band intensity ... [READ MORE]

Authors: J. K. Lawrence and A.C. Cadavid, CSU Northridge
Projects: Hinode/SOT

Publication Status: submitted to Solar Physics
Last Modified: 2009-07-30 11:14
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Deconstructing active region AR10961 using STEREO, Hinode, TRACE & SOHO      

Jane Benedetta Noglik   Submitted: 2008-07-28 08:15

Active region 10961 was observed over a five day period (2007 July 2-6) by instrumentation on-board STEREO, Hinode, TRACE and SOHO. As it progressed from Sun centre to the solar limb a comprehensive analysis of the EUV, X-ray and magnetic field data reveals clearly observable changes in the global nature of the region. Temperature analyses undertaken using STEREO EUVI double filter ratios and XRT single and combined filter ratios demonstrate an overall cooling of the region from between 1.6 - 3.0 MK to 1.0 - 2.0 MK over the five days. Similarly, Hinode EIS density measurements show a corresponding increase in density of 27 %. Moss, cool (1 MK) outer loop areas and hotter core loop regions were examined and compared with potential magnetic field extrapolations from SOHO MDI ... [READ MORE]

Authors: Jane B. Noglik, Robert W. Walsh & Rhona C. Maclean
Projects: Hinode/EIS,Hinode/XRT,SoHO-MDI,STEREO,TRACE

Publication Status: Submitted to ApJ
Last Modified: 2008-09-23 20:52
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Interaction between Granulation and Small-Scale Magnetic Flux Observed by Hinode      

Shuhong Yang   Submitted: 2009-05-11 00:05

With the polarimetric observations obtained by the Spectro-Polarimeter on board Hinode, we study the relationship between granular development and magnetic field evolution in the quiet Sun. 6 typical cases are displayed to exhibit interaction between granules and magnetic elements, and we have obtained the following results. (1) A granule develops centrosymmetrically when no magnetic flux emerges within the granular cell. (2) A granule develops and splits noncentrosymmetrically while flux emerges at an outer part of the granular cell. (3) Magnetic flux emergence as a cluster of mixed polarities is detected at the position of a granule as soon as the granule breaks up. (4) A dipole emerges accompanying with the development of a granule, and the two elements of the dipole root in the ... [READ MORE]

Authors: Jun Zhang, Shuhong Yang and Chunlan Jin
Projects: Hinode/SOT

Publication Status: Accepted by RAA
Last Modified: 2009-05-11 07:49
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Study on Triggering Process of Solar Flares Based on Hinode/SOT Observations      

Yumi Bamba   Submitted: 2013-09-21 06:19

We investigated four major solar flare events that occurred in active regions NOAA 10930 (December 13 and 14, 2006) and NOAA 11158 (February 13 and 15, 2011) by using data observed by the Solar Optical Telescope (SOT) onboard the Hinode satellite. To reveal the trigger mechanism of solar flares, we analyzed the spatio-temporal correlation between the detailed magnetic field structure and the emission image of the Ca H line at the central part of flaring regions for several hours prior to the onset of flares. We observed in all the flare events that the magnetic shear angle in the flaring regions exceeded 70 degrees, as well as that characteristic magnetic disturbances developed at the centers of flaring regions in the pre-flare phase. These magnetic disturbances can be classified into two ... [READ MORE]

Authors: Y. Bamba, K. Kusano, T. T. Yamamoto, and T. J. Okamoto
Projects: Hinode/SOT

Publication Status: in press.
Last Modified: 2013-09-25 17:53
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Evidence of Explosive Evaporation in a Microflare Observed by Hinode/EIS      

Feng Chen   Submitted: 2010-09-15 20:37

We present a detailed study of explosive chromospheric evaporation during a microflare which occurred on 2007 December 7 as observed with the EUV Imaging Spectrometer (EIS) onboard Hinode. We find temperature-dependent upflows for lines formed from 1.0 to 2.5 MK and downflows for lines formed from 0.05 to 0.63 MK in the impulsive phase of the flare. Both the line intensity and the nonthermal line width appear enhanced in most of the lines and are temporally correlated with the time when significant evaporation was observed. Our results are consistent with the numerical simulations of flare models, which take into account a strong nonthermal electron beam in producing the explosive chromospheric evaporation. The explosive evaporation observed in this microflare implies that the same ... [READ MORE]

Authors: F. Chen and M. D. Ding
Projects: Hinode/EIS

Publication Status: accepted to publish on the Astrophysical Journal
Last Modified: 2010-09-17 08:54
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Hinode observations and 3D magnetic structure of an X-ray bright point      

Caroline Alexander   Submitted: 2011-02-01 06:47

Aims: We present complete Hinode Solar Optical Telescope (SOT), X-Ray Telescope (XRT)and EUV Imaging Spectrometer (EIS) observations of an X-ray bright point (XBP) observed on the 10, 11 of October 2007 over its entire lifetime (~12 h). We aim to show how the measured plasma parameters of the XBP change over time and also what kind of similarities the X-ray emission has to a potential magnetic field model. Methods: Information from all three instruments on-board Hinode was used to study its entire evolution. XRT data was used to investigate the structure of the bright point and to measure the X-ray emission. The EIS instrument was used to measure various plasma parameters over the entire lifetime of the XBP. Lastly, the SOT was used to measure the magnetic field strength and provide a ... [READ MORE]

Authors: Alexander, C. E.; Del Zanna, G.; Maclean, R. C.
Projects: Hinode/EIS,Hinode/SOT,Hinode/XRT

Publication Status: A&A (published)
Last Modified: 2011-02-02 07:02
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Observations of Chromospheric Anemone Jets with Hinode SOT and Hida Ca II Spectroheliogram      

Satoshi Morita   Submitted: 2010-02-11 09:04

We present the first simultaneous observations of chromospheric ''anemone'' jets in solar active regions with Hinode SOT Ca II H broadband filetergram and Ca II K spetroheliogram on the Domeless Solar Telescope (DST) at Hida Observatory. During the coordinated observation, 9 chromospheric anemone jets were simultaneously observed with the two instruments. These observations revealed three important features, i.e.: (1) the jets are generated in the lower chromosphere, i.e. these cannot be seen in Ca II K3, (2) the length and lifetime of the jets are 0.4-5 Mm and 40-320 sec, (3) the apparent velocity of the jets with Hinode SOT are 3-24 km/s, while Ca II K3 component at the jets show blueshifts (in 5 events) in the range of 2- 6 km/s. The chromospheric anemone jets are associated with mixed ... [READ MORE]

Authors: Morita, S., Shibata, K., Ueno, S., Ichimoto, K., Kitai, R., and Otsuji, K.
Projects: Hinode/SOT

Publication Status: PASJ (accepted)
Last Modified: 2010-02-11 13:33
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Hinode/EIS observations of propagating low-frequency slow magnetoacoustic waves in fan-like coronal loops      

Tongjiang Wang   Submitted: 2009-08-03 12:43

We report the first observation of multiple-periodic propagating disturbances along a fan-like coronal structure simultaneously detected in both intensity and Doppler shift in the Fe XII 195 A line with the EUV Imaging Spectrometer (EIS) onboard Hinode. A new application of coronal seismology is provided based on this observation. We analyzed the EIS sit-and-stare mode observation of oscillations using the running difference and wavelet techniques. Two harmonics with periods of 12 and 25 min are detected. We measured the Doppler shift amplitude of 1-2 km/s, the relative intensity amplitude of 3%-5% and the apparent propagation speed of 100-120 km/s. The amplitude relationship between intensity and Doppler shift oscillations provides convincing evidence that these propagating features are ... [READ MORE]

Authors: T. J. Wang, L. Ofman, J. M. Davila, J. T. Mariska
Projects: Hinode/EIS,TRACE

Publication Status: A&A Letter, 2009, in press
Last Modified: 2009-08-04 08:07
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The Hinode /XRT Full-Sun Image Corrections and the Improved Synoptic Composite Image Archive      

Aki Takeda   Submitted: 2015-12-27 22:14

The XRT Synoptic Composite Image Archive (SCIA) is a storage and gallery of X-ray full-Sun images obtained through the synoptic program of the X-Ray Telescope (XRT) onboard the Hinode satellite. The archived images provide a quick history of solar activity through the daily and monthly layout pages and long-term data for morphological and quantitative studies of the X-ray corona. This article serves as an introduction to the SCIA, i.e., to the structure of the archive and specification of the data products included therein. We also describe a number of techniques used to improve the quality of the archived images: preparation of composite images to increase intensity dynamic range, removal of dark spots that are due to contaminants on the CCD, and correction of the visible stray light ... [READ MORE]

Authors: Takeda, A., Yoshimura, K., Saar, S.
Projects: Hinode/XRT

Publication Status: SolarPhysics(in press)
Last Modified: 2015-12-30 12:41
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Hinode XRT observations of a long-lasting coronal sigmoid      

David E McKenzie   Submitted: 2009-05-19 16:04

Aims: Coronal sigmoids are important sources of eruptions into interplanetary space, and a handful of models have been proposed to explain their characteristic S shape. However, the coronal X-ray images available to date have generally not had sufficient resolution to distinguish between these models. The goal of the present investigation is to determine whether the new observations from Hinode can help us to make such a distinction. Methods: We present the first observations of a persistent coronal sigmoid obtained with the Hinode X-Ray Telescope (XRT). The excellent angular resolution of XRT (1 arcsec per pixel) and the sigmoid's location near disk center combined to provide an unprecedented view of the formation and eruption of this phenomenon. We compared the observed ... [READ MORE]

Authors: D. E. McKenzie and R. C. Canfield
Projects: Hinode/XRT

Publication Status: Published in Astronomy & Astrophysics (2008), v.481, L65-L68
Last Modified: 2009-05-20 09:24
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Signatures of Alfv?en waves in the polar coronal holes as seen by EIS/Hinode      

Dipankar Banerjee   Submitted: 2009-06-24 22:21

Context. We diagnose the properties of the plume and interplume regions in a polar coronal hole and the role of waves in the acceleration of the solar wind. Aims. We attempt to detect whether Alfven waves are present in the polar coronal holes through variations in EUV line widths. Methods. Using spectral observations performed over a polar coronal hole region with the EIS spectrometer on Hinode, we study the variation in the line width and electron density as a function of height. We use the density sensitive line pairs of Fe xii 186.88 A & 195.119 A and Fe xiii 203.82 A & 202.04 A . Results. For the polar region, the line width data show that the nonthermal line-of-sight velocity increases from 26 km/s at 1000 above the limb to 42 km/s some 15000 (i.e. 110,000 km) above the limb. ... [READ MORE]

Authors: D. Banerjee, D. P?erez-Su?arez, and J.G. Doyle
Projects: Hinode/EIS

Publication Status: A&A Letters (in press)
Last Modified: 2009-06-25 13:25
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Hinode EIS Observations of a Limb Active Region      

Brendan O'Dwyer   Submitted: 2010-08-31 13:29

We have carried out a study of an active region close to the solar limb using observations from the Extreme-ultraviolet Imaging Spectrometer (EIS) and the X-Ray Telescope (XRT) on board Hinode. The electron density and temperature distributions of the coronal emission have been determined using emission line intensity ratios. Differential emission measure (DEM) analysis and the emission measure (EM) loci technique were used to examine the thermal structure of the emitting plasma as a function of distance from the limb. The highest temperature and electron density values are found to be located in the core of the active region, with a peak electron number density value of 1.9 x 10^10 cm^-3 measured using the Fe XII 186.887 A to 192.394 A line intensity ratio. The plasma along the line of ... [READ MORE]

Authors: B. O'Dwyer, G. Del Zanna, H. E. Mason, Alphonse C. Sterling, D. Tripathi, P. R. Young
Projects: Hinode/EIS,Hinode/XRT

Publication Status: Accepted for publication in Astronomy and Astrophysics.
Last Modified: 2010-09-01 08:07
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Hot Plasma in Non-Flaring Active Regions Observed by the Extreme-ultraviolet Imaging Spectrometer on Hinode      

Yuan-Kuen Ko   Submitted: 2009-03-20 07:01

The Extreme-ultraviolet Imaging Spectrometer (EIS) on the Hinode spacecraft obtains high resolution spectra of the solar atmosphere in two wavelength ranges: 170 - 210 and 250 - 290 angstroms. These wavelength regions contain a wealth of emission lines covering temperature regions from the chromosphere/transition region (e.g., He II, Si VII) up to flare temperatures (Fe XXIII, Fe XXIV). Of particular interest for understanding coronal heating is a line of Ca XVII at 192.858 angstroms, formed near a temperature of 6 million degrees. However, this line is blended with two Fe XI and six O V lines. In this paper we discuss a specific procedure to extract the Ca XVII line from the blend. We have performed this procedure on the raster data of five active regions and a limb flare, and ... [READ MORE]

Authors: Yuan-Kuen Ko, George A. Doschek, Harry P. Warren, Peter R. Young
Projects: Hinode/EIS

Publication Status: ApJ (in press)
Last Modified: 2009-03-20 09:15
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Differential Emission Measures from the Regularized Inversion of Hinode and SDO data      

Iain Hannah   Submitted: 2012-01-23 11:24

We develop and apply an enhanced regularization algorithm, used in RHESSI X-ray spectral analysis, to constrain the ill-posed inverse problem that is determining the DEM from solar observations. We demonstrate this computationally fast technique applied to a range of DEM models simulating broadband imaging data from SDO/AIA and high resolution line spectra from Hinode/EIS, as well as actual active region observations with Hinode/EIS and XRT. As this regularization method naturally provides both vertical and horizontal (temperature resolution) error bars we are able to test the role of uncertainties in the data and response functions. The regularization method is able to successfully recover the DEM from simulated data of a variety of model DEMs (single Gaussian, multiple Gaussians and ... [READ MORE]

Authors: I. G. Hannah, E. P. Kontar
Projects: Hinode/EIS,Hinode/XRT,SDO-AIA,SDO-EVE

Publication Status: A&A (accepted)
Last Modified: 2012-01-24 11:24
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Structure and Dynamics of Quiescent Filament Channels Observed by Hinode/XRT and STEREO/EUVI      

Yingna Su   Submitted: 2010-08-06 08:03

We present a study on the structure and dynamics of quiescent filament channels observed by Hinode/XRT and STEREO/EUVI at the solar minimum 23/24 from December 2006 to December 2008. For 12 channels identified on the solar disk (Group I channels), we find that the morphology of the structure on the two sides of the channel is asymmetric in both X-rays and EUV: eastern side has curved features while the western side has straight features. We interpret the results in terms of a magnetic flux rope model. The asymmetry in the morphology is due to the variation in axial flux of the flux rope along the channel, which causes the field lines from one polarity to turn into the flux rope (curved feature), while the field lines from the other polarity are connected to very distant sources ... [READ MORE]

Authors: Yingna Su, Adriaan van Ballegooijen, Leon Golub
Projects: Hinode/XRT

Publication Status: 2010 ApJ, 721, 901
Last Modified: 2011-04-06 09:08
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The Structure and Dynamics of a Bright Point as seen with Hinode, SoHO and TRACE      

David Perez-Suarez   Submitted: 2008-10-09 08:49

Our aim is to determine the plasma properties of a coronal bright point and compare its magnetic topology extrapolated from magnetogram data with its appearance in X-ray images. We analyse spectroscopic data obtained with EIS/Hinode, Ca II H and G-band images from SOT/Hinode, UV images from TRACE, X-ray images from XRT/Hinode and high-resolution/high-cadence magnetogram data from MDI/SoHO. The BP comprises several coronal loops as seen in the X-ray images, while the chromospheric structure consists of tens of small bright points as seen in Ca II H. An excellent correlation exists between the Ca II BPs and increases in the magnetic field, implying that the Ca II H passband is a good indicator for the concentration of magnetic flux. Doppler velocities between 6 and 15 km/s are ... [READ MORE]

Authors: D. P'erez-Su'arez, R.C. Maclean, J.G. Doyle and M.S. Madjarska
Projects: Hinode/EIS,Hinode/SOT,Hinode/XRT,SoHO-EIT,SoHO-MDI,TRACE

Publication Status: A&A (in press)
Last Modified: 2008-10-09 08:49
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Doppler Shift, Intensity, and Density Oscillations Observed with the EUV Imaging Spectrometer on Hinode      

John Mariska   Submitted: 2010-03-02 08:15

Low-amplitude Doppler-shift oscillations have been observed in coronal emission lines in a number of active regions with the EUV Imaging Spectrometer (EIS) on the Hinode satellite. Both standing and propagating waves have been detected and many periods have been observed, but a clear picture of all the wave modes that might be associated with active regions has not yet emerged. In this study, we examine additional observations obtained with EIS in plage near an active region on 2007 August 22--23. We find Doppler-shift oscillations with amplitudes between 1 and 2 km/s in emission lines ranging from Fe XI 188.23 Angstroms, which is formed at log T = 6.07 to Fe XV 284.16 Angstroms, which is formed at log T = 6.32. Typical periods are near 10 minutes. We also observe intensity and density ... [READ MORE]

Authors: Mariska, John T. and Muglach, K.
Projects: Hinode/EIS

Publication Status: ApJ (in press)
Last Modified: 2010-03-02 09:25
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Coronal magnetic field measurement using loop oscillations observed by Hinode/EIS      

Tom Van Doorsselaere   Submitted: 2008-06-12 09:29

We report the first spectroscopic detection of a kink MHD oscillation of a solar coronal structure, made with the Extreme-Ultraviolet Imaging Spectrometer (EIS) on the recently launched Japanese Hinode satellite. The detected oscillation has an amplitude of 1 km/s in the Doppler shift of the FeXII 195Å spectral line (1.3 MK), and a period of 296 s. The unique combination of EIS's spectroscopic and imaging abilities allows us to simultaneously measure the mass density and length of oscillating loop. It allows us to directly measure the magnitude of the local magnetic field, the fundamental coronal plasma parameter, as 39±8 G, with unprecedented accuracy. This proof-of-concept makes EIS an exclusive instrument for the full scale implementation of the MHD coronal seismological ... [READ MORE]

Authors: T. Van Doorsselaere, V.M. Nakariakov, P.R. Young, E. Verwichte
Projects: Hinode/EIS

Publication Status: A&A Letters, accepted
Last Modified: 2008-09-23 20:59
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Chromospheric signatures of small-scale flux emergence as observed with NST and Hinode instruments      

Vasyl Yurchyshyn   Submitted: 2010-12-10 10:19

With the ever increasing influx of high resolution images of the solar surface obtained at a multitude of wavelengths, various processes occurring at small spatial scales have become a greater focus of our attention. Complex small-scale magnetic fields have been reported that appear to have enough stored to heat the chromosphere. While significant progress has been made in understanding small-scale phenomena, many specifics remain elusive. We present here a detailed study of a single event of cancellation and associated chromospheric activity. Based on New Solar Telescope Ha data and Hinode photospheric line-of-sight magnetograms and Ca II H images we report the following. 1) Careful consideration of the magnetic environment at the cancellation site sharpened our understanding of the ... [READ MORE]

Authors: V. B. Yurchyshyn, P.R. Goode, V. I. Abramenko, J. Chae, W. Cao, A. Andic, K. Ahn
Projects: Hinode/SOT

Publication Status: Astrophysical Journal, Volume 722, Issue 2, pp. 1970-1976 (2010)
Last Modified: 2010-12-10 10:34
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Statistical Analysis of Current Helicity and Twist in Solar Active Regions over the Phases of the Solar Cycle Using the Spectro-Polarimeter Data of Hinode      

Kenichi Otsuji   Submitted: 2014-10-29 19:10

Current helicity and twist of solar magnetic fields are important quantities to characterize the dynamo mechanism working in the convection zone of the Sun. We have carried out a statistical study on the current helicity of solar active regions observed with the Spectro-Polarimeter (SP) of Hinode Solar Optical Telescope (SOT). We used SOT-SP data of 558 vector magnetograms of a total of 80 active regions obtained from 2006 to 2012. We have applied spatial smoothing and division of data points into weak and strong field ranges to compare the contributions from different scales and field strengths. We found that the current helicity follows the so-called hemispheric sign rule when the weak magnetic fields (absolute field strength $< 300$ gauss) are considered and no smoothing is ... [READ MORE]

Authors: Kenichi Otsuji, Takashi Sakurai and Kirill Kuzanyan
Projects: Hinode/SOT

Publication Status: accepted
Last Modified: 2014-10-30 09:49
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Transverse oscillations of loops with coronal rain observed by Hinode/SOT      

Patrick Antolin   Submitted: 2011-05-12 02:26

The condensations composing coronal rain, falling down along loop-like structures observed in cool chromospheric lines such as H$alpha$ and ion{Ca}{2} H, have long been a spectacular phenomenon of the solar corona. However, considered a peculiar sporadic phenomenon, it has not received much attention. This picture is rapidly changing due to recent high resolution observations with instruments such as extit{Hinode}/SOT, CRISP of extit{SST} and extit{SDO}. Furthermore, numerical simulations have shown that coronal rain is a loss of thermal equilibrium of loops linked to footpoint heating. This result has highlighted the importance that coronal rain can play in the field of coronal heating. In this work, we further stress the importance of coronal rain by showing the role it can play in ... [READ MORE]

Authors: Patrick Antolin and Erwin Verwichte
Projects: Hinode/SOT

Publication Status: Accepted for publication in The Astrophysical Journal
Last Modified: 2011-05-12 15:06
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Quasi-Periodic Fluctuations and Chromospheric Evaporation in a Solar Flare Ribbon Observed by Hinode/EIS, IRIS, and RHESSI      

Andrew Inglis   Submitted: 2016-10-17 11:44

The Hinode/Extreme-ultraviolet Imaging Spectrometer (EIS) obtained rapid cadence (11.2 s) EUV stare spectra of an M7.3 flare ribbon in AR 12036 on 2014 April 18. Quasi-periodic (P ≈ 75.6 ? 9.2 s) intensity fluctuations occurred in emission lines of O iv, Mg vi, Mg vii, Si vii, Fe xiv, and Fe xvi during the flare's impulsive rise, and ended when the maximum intensity in Fe xxiii was reached. The profiles of the O iv?Fe xvi lines reveal that they were all redshifted during most of the interval of quasi-periodic intensity fluctuations, while the Fe xxiii profile revealed multiple components including one or two highly blueshifted ones. This indicates that the flare underwent explosive chromospheric evaporation during its impulsive rise. Fluctuations in the relative Doppler velocities ... [READ MORE]

Authors: J. W. Brosius, A. N. Daw and A. R. Inglis
Projects: Hinode/EIS,IRIS,RHESSI

Publication Status: The Astrophysical Journal, 830, 101, 2016
Last Modified: 2016-10-19 13:08
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Flows and Non-thermal Velocities in Solar Active Regions Observed with the Extreme-ultraviolet Imaging Spectrometer on Hinode: A Tracer of Active Region Sources of Heliospheric Magnetic Fields?      

George Doschek   Submitted: 2008-07-21 10:06

From Doppler velocity maps of active regions constructed from spectra obtained by the Extreme-ultraviolet Imaging Spectrometer (EIS) on the Hinode spacecraft we observe large areas of outflow (20-50 km/s) that can persist for at least a day. These outflows occur in areas of active regions that are faint in coronal spectral lines formed at typical quiet Sun and active region temperatures. The outflows are positively correlated with non-thermal velocities in coronal plasmas. The bulk mass motions and non-thermal velocities are derived from spectral line centroids and line widths, mostly from a strong line of Fe XII at 195.12 Angstroms. The electron temperature of the outflow regions estimated from an Fe XIII to Fe XII line intensity ratio is about 1.2-1.4 MK. The electron density of the ... [READ MORE]

Authors: G. A. Doschek, H. P. Warren, J. T. Mariska, K. Muglach, J. L. Culhane, H. Hara, and T. Watanabe
Projects: Hinode/EIS

Publication Status: ApJ accepted
Last Modified: 2008-09-23 20:56
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Signature of slow acoustic oscillations in a non-flaring loop observed by EIS/Hinode      

Dr. A. K. Srivastava   Submitted: 2009-09-10 22:04

egin{abstract} % Text of abstract We study intensity oscillations near the apex of a coronal loop to find the signature of MHD oscillations.We analyse the time series of the strongest Fe XII 195.12 AA image data, observed by $40''$ SLOT of the EUV Imaging Spectrometer (EIS) onboard the Hinode spacecraft. Using a standard wavelet tool, we produce power spectra of intensity oscillations at location $'$L$_{3}$$'$ near the apex of a clearly visible coronal loop. We detect intensity oscillations of a period of $approx 322,s$ with a probability of 96 \%. This oscillation period of $approx$ 322 s is found to be in good agreement with theory of the second harmonics of standing slow acoustic oscillations of $P_{2^{nd} slow} approx 313 pm 31,s$. We detect, for the first time, ... [READ MORE]

Authors: A.K. Srivastava; B.N. Dwivedi
Projects: Hinode/EIS

Publication Status: New Astronomy, 2010, Vol. 15, pp. 8-15
Last Modified: 2009-09-11 08:18
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Hinode and IRIS observations of the magnetohydrodynamic waves propagating from the photosphere to the chromosphere in a sunspot      

Ryuichi Kanoh   Submitted: 2016-08-18 21:34

Magnetohydrodynamic (MHD) waves have been considered as energy sources for heating the solar chromosphere and the corona. Although MHD waves have been observed in the solar atmosphere, there are lack of quantitative estimates on the energy transfer and dissipation in the atmosphere. We performed simultaneous Hinode and IRIS observations of a sunspot umbra to derive the upward energy fluxes at two different atmospheric layers (photosphere and lower transition region) and estimate the energy dissipation. The observations revealed some properties of the observed periodic oscillations in physical quantities, such as their phase relations, temporal behaviors, and power spectra, making a conclusion that standing slow-mode waves are dominant at the photosphere with their high frequency leakage, ... [READ MORE]

Authors: Ryuichi Kanoh, Toshifumi Shimizu, Shinsuke Imada
Projects: Hinode/SOT,IRIS

Publication Status: accepted for publication in ApJ
Last Modified: 2016-08-23 16:20
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Evolution of the Sheared Magnetic Fields of two X-class Flares Observed by Hinode/XRT      

Yingna Su   Submitted: 2007-08-17 09:39

We present multi-wavelength observations of the evolution of the sheared magnetic fields in NOAA Active Region 10930, where two X-class flares occurred on 2006 December 13 and December 14, respectively. Observations made with the X-ray Telescope (XRT) and the Solar Optical Telescope (SOT) aboard Hinode suggest that the gradual formation of the sheared magnetic fields in this active region is caused by the rotation and west-to-east motion of an emerging sunspot. In the pre-flare phase of the two flares, XRT shows several highly sheared X-ray loops in the core field region, corresponding to a filament seen in the TRACE EUV observations. XRT observations also show that part of the sheared core field erupted, and another part of the sheared core field stayed behind during the flares, which ... [READ MORE]

Authors: Yingna Su, Leon Golub, Adriaan Van Ballegooijen, Edward Deluca, Kathy Reeves, Taro Sakao, Ryohei Kano, Noriyuki Narukage, and Kiyoto Shibasaki
Projects: Hinode/XRT

Publication Status: 2007, PASJ, 59, 785
Last Modified: 2011-04-06 12:47
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Establishing a Connection Between Active Region Outflows and the Solar Wind: Abundance Measurements with EIS/Hinode      

David Brooks   Submitted: 2012-04-12 21:50

One of the most interesting discoveries from Hinode is the presence of persistent high-temperature high-speed outflows from the edges of active regions (ARs). EUV imaging spectrometer (EIS) measurements indicate that the outflows reach velocities of 50 km s?1 with spectral line asymmetries approaching 200 km s?1. It has been suggested that these outflows may lie on open field lines that connect to the heliosphere, and that they could potentially be a significant source of the slow speed solar wind. A direct link has been difficult to establish, however. We use EIS measurements of spectral line intensities that are sensitive to changes in the relative abundance of Si and S as a result of the first ionization potential (FIP) effect, to measure the chemical composition in the outflow regions ... [READ MORE]

Authors: Brooks, David H., Warren, Harry P.
Projects: Hinode/EIS

Publication Status: Published in ApJ, 727, L13 (2011)
Last Modified: 2012-04-16 09:52
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Two Types of Dynamic Cool Coronal Structures Observed with STEREO and HINODE      

Jun Zhang   Submitted: 2009-09-09 21:23

Solar coronal loops show significant plasma motions during their formation and eruption stages. Dynamic cool coronal structures, on the other hand, are often observed to propagate along coronal loops. In this paper, we report on the discovery of two types of dynamic cool coronal structures, and characterize their fundamental properties. Using the EUV 304 angstrom images from the Extreme UltraViolet Imager (EUVI) telescope on the Solar TErrestrial RElation Observatory (STEREO) and the Ca II filtergrams from the Solar Optical Telescope (SOT) instrument on HINODE, we study the evolution of an EUV arch and the kinematics of cool coronal structures. The EUV 304 angstrom observations show that a missile-like plasmoid moves along an arch-shaped trajectory, with an average velocity of 31 km/s. ... [READ MORE]

Authors: J. Zhang and L. P. Li
Projects: Hinode/SOT,STEREO

Publication Status: accepted by RAA
Last Modified: 2009-09-10 08:14
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Plasma diagnostics of an EIT wave observed by Hinode/EIS and SDO/AIA      

Astrid Veronig   Submitted: 2011-11-16 01:46

We present plasma diagnostics of an EIT wave observed with high cadence in Hinode/EIS sit-and-stare spectroscopy and SDO/AIA imagery obtained during the HOP-180 observing campaign on 2011 February 16. At the propagating EIT wave front, we observe downward plasma flows in the EIS Fe XII, Fe XIII, and Fe XVI spectral lines (log T ~ 6.1-6.4) with line-of-sight (LOS) velocities up to 20 km/s. These red-shifts are followed by blue-shifts with upward velocities up to -5 km/s indicating relaxation of the plasma behind the wave front. During the wave evolution, the downward velocity pulse steepens from a few km/s up to 20 km/s and subsequently decays, correlated with the relative changes of the line intensities. The expected increase of the plasma densities at the EIT wave front estimated from ... [READ MORE]

Authors: A.M. Veronig, P. G?m?ry, I.W. Kienreich, N. Muhr, B. Vrsnak, M. Temmer, H.P. Warren
Projects: Hinode/EIS,SDO-AIA

Publication Status: ApJ Lett., in press
Last Modified: 2011-11-16 13:19
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A Hot Microflare Observed with RHESSI and Hinode      

Ryan Milligan   Submitted: 2008-05-05 09:23

RHESSI and Hinode observations of a GOES B-class flare are combined to investigate the origin of 15 MK plasma. The absence of any detectable hard X-ray emission coupled with weak blueshifted emission lines (indicating upward velocities averaging only 14 km/s) suggests that this was a result of direct heating in the corona, as opposed to nonthermal electron precipitation causing chromospheric evaporation. These findings are in agreement with a recent hydrodynamical simulation of microflare plasmas which found that higher temperatures can be attained when less energy is used to accelerate electrons out of the thermal distribution. In addition, unusual redshifts in the 2 MK Fe XV line (indicating downward velocities of ∼14 km/s) were observed cospatial with one of the flare ribbons ... [READ MORE]

Authors: Ryan O. Milligan
Projects: Hinode/EIS,Hinode/SOT,Hinode/XRT,RHESSI

Publication Status: ApJL, accepted
Last Modified: 2008-09-23 21:02
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Magnetic flux cancellation associated with a recurring solar jet observed with Hinode, RHESSI, and STEREO/EUVI      

Cristina Chifor   Submitted: 2008-09-01 07:42

Aims. We study the physical properties of a recurring solar active region jet observed in X-rays and extreme-ultraviolet (EUV). Methods. Multi-wavelength data from all three instruments on board Hinode were analysed. X-ray imaging and spectroscopy of the microflaring emission associated with the jets was performed with the Reuven Ramaty High Energy Spectroscopic Imager (RHESSI). Associated EUV jets were observed with the Sun Earth Connection Coronal and Heliospheric Investigation (SECCHI)/Extreme Ultraviolet Imager (EUVI) on board STEREO. Results. We found a correlation between recurring magnetic flux cancellation close to a pore, the X-ray jet emission, and associated Ca II H ribbon brightenings. We estimated the lower limit for the decrease in magnetic energy associated with the ... [READ MORE]

Authors: C. Chifor, H. Isobe, H. E. Mason, I. G. Hannah, P. R. Young, G. Del Zanna, S. Krucker, K. Ichimoto, Y. Katsukawa, T. Yokoyama
Projects: Hinode/EIS,Hinode/SOT,Hinode/XRT,RHESSI,STEREO

Publication Status: A&A, in press
Last Modified: 2008-09-02 07:55
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EUV lines observed with EIS/Hinode in a solar prominence      

Nicolas Labrosse   Submitted: 2011-05-11 15:27

We report on observations of a solar prominence obtained on 26 April 2007 using the Extreme Ultraviolet Imaging Spectrometer on Hinode. Several regions within the prominence are identified for further analysis. Selected profiles for lines with formation temperatures between log(T)=4.7-6.3, as well as their integrated intensities, are given. The line profiles are discussed. We pay special attention to the He II line which is blended with coronal lines. Our analysis confirms that depression in EUV lines can be interpreted by two mechanisms: absorption of coronal radiation by the hydrogen and neutral helium resonance continua, and emissivity blocking. We present estimates of the He II line integrated intensity in different parts of the prominence according to different scenarios for the ... [READ MORE]

Authors: Nicolas Labrosse, Brigitte Schmieder, Petr Heinzel, Tetsuya Watanabe
Projects: Hinode/EIS,Hinode/SOT,Hinode/XRT

Publication Status: Accepted, A&A
Last Modified: 2011-05-12 15:06
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Hinode/XRT and STEREO observations of a diffuse coronal ''wave''-CME-dimming event      

Gemma Attrill   Submitted: 2009-09-17 12:39

We report on observations of the first diffuse coronal wave detected by Hinode/XRT. The event occurred near the West solar limb on 23 May 2007, originating from active region (AR) 10956 and was associated with a coronal mass ejection (CME) and coronal dimmings. The bright emission forming the coronal wave expanded both to the East and South of the AR. We use XRT and STEREO Behind (B) data combined with a potential magnetic field extrapolation to derive an understanding of the global magnetic field connectivity. The brightenings observed East and South of the source AR are generated by two different physical processes, due to the distinct magnetic environments in these regions. We attribute the brightening to the East of the AR to compression and channelling of the plasma along ... [READ MORE]

Authors: Gemma D. R. Attrill, Alexander J. Engell, Meredith J. Wills-Davey, Paolo Grigis and Paola Testa
Projects: Hinode/XRT,STEREO

Publication Status: ApJ (in press)
Last Modified: 2009-09-18 10:37
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Hinode/EIS Spectroscopic Validation of Very Hot Plasma Imaged with the Solar Dynamics Observatory in Non-flaring Active Region Cores      

Fabio Reale   Submitted: 2012-04-27 08:52

We use coronal imaging observations with the Solar Dynamics Observatory/Atmospheric Imaging Assembly (AIA), and Hinode/Extreme-ultraviolet Imaging Spectrometer (EIS) spectral data to explore the potential of narrowband EUV imaging data for diagnosing the presence of hot (T >~ 5 MK) coronal plasma in active regions. We analyze observations of two active regions (AR 11281, AR 11289) with simultaneous AIA imaging and EIS spectral data, including the Ca XVII line (at 192.8 A), which is one of the few lines in the EIS spectral bands sensitive to hot coronal plasma even outside flares. After careful co-alignment of the imaging and spectral data, we compare the morphology in a three-color image combining the 171, 335, and 94 A AIA spectral bands, with the image obtained for Ca XVII emission from ... [READ MORE]

Authors: Testa, P., Reale, F.
Projects: Hinode/EIS,SDO-AIA

Publication Status: ApJ Letters, 2012, 750, L10
Last Modified: 2012-04-27 09:07
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Flare Physics in the Hinode Era (Keynote)      

David E McKenzie   Submitted: 2009-05-19 16:13

Hinode's manifest of instrumentation was conceived to investigate the magnetic connections through the photosphere, lower atmosphere, and corona. The complementarity of the instruments is indeed useful, as demonstrated in numerous flares and eruptions in just the first two years of operation. I will review some of the findings from Hinode's observations of flares to date. It is true, of course, that Hinode's capabilities have evolved since launch. These changes cause the planning of observations to be more complex, and the analysis to be less straightforward; but they do not diminish Hinode's ability to produce important observations of solar flares. On the contrary, Hinode is poised to make truly surprising discoveries. I will explain why this is so, and why we should look ... [READ MORE]

Authors: David E. McKenzie
Projects: Hinode/EIS,Hinode/SOT,Hinode/XRT

Publication Status: Accepted for publication in Hinode-2 proceedings.
Last Modified: 2009-05-20 09:24
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Velocity Characteristics of Evaporated Plasma Using Hinode/EIS     

Ryan Milligan   Submitted: 2009-02-25 09:58

This abstract was corrupted following database problems and is being recovered. It will be restored as quickly as possible. Any questions, please send them to Alisdair. Sorry for any incovenience.


Authors: Ryan O. Milligan, Brian R. Dennis
Projects: Hinode/EIS,RHESSI

Publication Status: ApJ (accepted)
Last Modified: 2012-01-24 13:33
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Chromospheric Evaporation in Solar Flare Loop Strands Observed with the Extreme-ultraviolet Imaging Spectrometer Aboard Hinode     

Jeffrey Brosius   Submitted: 2012-12-28 09:04

The entire profile of the Fe XXIII line at 263.8 Angstroms, formed at temperature around 14 MK, was blueshifted by an upward velocity -122 +/- 33 km/s when it was first detected by the Extreme-ultraviolet Imaging Spectrometer (EIS) operating in rapid cadence (11.18 s) stare mode during a C1 solar flare. The entire profile became even more blueshifted over the next two exposures, when the upward velocity reached its maximum of -208 +/- 14 km/s before decreasing to zero over the next 12 exposures. After that, a weak, secondary blueshifted component appeared for 5 exposures, reached a maximum upward velocity of -206 +/- 33 km/s, and disappeared after the maximum line intensity (stationary plus blueshifted) was achieved. Velocities were measured relative to the intense stationary profile ... [READ MORE]

Authors: Brosius, J. W.
Projects: Hinode/EIS,SDO-AIA,SoHO-CDS

Publication Status: ApJ, 762, 133 (2013)
Last Modified: 2012-12-28 09:17
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SDO AIA and Hinode EIS observations of `warm' loops     

Giulio Del Zanna   Submitted: 2011-09-08 06:38

This abstract was corrupted following database problems and is being recovered. It will be restored as quickly as possible. Any questions, please send them to Alisdair. Sorry for any incovenience.


Authors: Del Zanna, G, O' Dwyer, B., Mason, H.E.
Projects: Hinode/EIS,SDO-AIA

Publication Status: A&A, accepted
Last Modified: 2011-09-08 09:32
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Thermal Properties of A Solar Coronal Cavity Observed with the X-ray Telescope on Hinode     

Kathy Reeves   Submitted: 2011-11-03 15:20

This abstract was corrupted following database problems and is being recovered. It will be restored as quickly as possible. Any questions, please send them to Alisdair. Sorry for any incovenience.


Authors: Reeves, K. K., Gibson, S. E., Kucera, T. A., Hudson, H. S. and Kano, R.
Projects: Hinode/XRT,SoHO-EIT,STEREO

Publication Status: Submitted to ApJ
Last Modified: 2011-11-03 15:21
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Benchmarking atomic data for the CHIANTI atomic database: coronal lines observed by Hinode EIS     

Giulio Del Zanna   Submitted: 2011-09-14 05:24

This abstract was corrupted following database problems and is being recovered. It will be restored as quickly as possible. Any questions, please send them to Alisdair. Sorry for any incovenience.


Authors: Del Zanna, G.
Projects: Hinode/EIS

Publication Status: A&A, in press
Last Modified: 2011-09-14 12:59
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Observations of Plasma Upflow in a Warm Loop with Hinode/EIS     

Durgesh Tripathi   Submitted: 2012-06-17 08:15

A complete understanding of Doppler shift in active region loops can help probe the basic physical mechanism involved into the heating of those loops. Here we present observations of upflows in coronal loops detected in a range of temperature temperatures (log, T=5.8 - 6.2). The loop was not discernible above these temperatures. The speed of upflow was strongest at the footpoint and decreased with height. The upflow speed at the footpoint was about 20 km s-1 in FeVIII which decreased with temperature being about 13 km s-1 in FeX, about 8 km s-1 in FeXII and about 4 km s-1 in FeXIII. To the best of our knowledge this is the first observation providing evidence of ... [READ MORE]

Authors: Durgesh Tripathi, Helen E. Mason, Giulio Del Zanna, and Steve Bradshaw
Projects: Hinode/EIS

Publication Status: Accepted for publication in ApJ Letters
Last Modified: 2012-06-17 12:31
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The first measurement of the adiabatic index in the solar corona using time-dependent spectroscopy of Hinode/EIS observations     

Tom Van Doorsselaere   Submitted: 2011-06-24 07:53

This abstract was corrupted following database problems and is being recovered. It will be restored as quickly as possible. Any questions, please send them to Alisdair. Sorry for any incovenience.


Authors: Van Doorsselaere T., Wardle N., Del Zanna G., Jansari K., Verwichte E., and Nakariakov V.M.
Projects: Hinode/EIS

Publication Status: published
Last Modified: 2011-06-24 11:54
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Anatomy of a solar flare: measurements of the December 14, 2006 X-class flare with GONG, Hinode and RHESSI     

Sarah Matthews   Submitted: 2011-07-12 09:48

This abstract was corrupted following database problems and is being recovered. It will be restored as quickly as possible. Any questions, please send them to Alisdair. Sorry for any incovenience.


Authors: Sarah Matthews, Sergei Zharkov & Valentina Zharkova
Projects: Hinode/SOT,TRACE,RHESSI,GONG

Publication Status: ApJ, In press
Last Modified: 2011-07-12 11:14
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Underflight calibration of SOHO/CDS and Hinode/EIS with EUNIS-07    

Tongjiang Wang   Submitted: 2011-09-30 09:49

Flights of Goddard Space Flight Center's Extreme-Ultraviolet Normal-Incidence Spectrograph (EUNIS) sounding rocket in 2006 and 2007 provided updated radiometric calibrations for SOHO/CDS and Hinode/EIS. EUNIS carried two independent imaging spectrographs covering wavebands of 300-370 A in first order and 170-205 A in second order. After each flight, end-to-end radiometric calibrations of the rocket payload were carried out in the same facility used for pre-launch calibrations of CDS and EIS. During the 2007 flight, EUNIS, SOHO CDS and Hinode EIS observed the same solar locations, allowing the EUNIS calibrations to be directly applied to both CDS and EIS. The measured CDS NIS 1 line intensities calibrated with the standard (version 4) responsivities with the standard long-term ... [READ MORE]

Authors: Tongjiang Wang, Roger J. Thomas, Jeffrey W. Brosius, Peter R. Young, Douglas M. Rabin, Joseph M. Davila, Giulio Del Zanna
Projects: EUNIS

Publication Status: accepted by ApJ Supplement, publication in December 2011, V197-2 issue
Last Modified: 2011-09-30 10:49
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Mass and energy of erupting solar plasma observed with the X-Ray Telescope on Hinode    

Jin-Yi Lee   Submitted: 2014-11-11 06:05

We investigate seven eruptive plasma observations by Hinode/XRT. Their corresponding EUV and/or white light CME features are visible in some events. Five events are observed in several passbands in X-rays, which allows the determination of the eruptive plasma temperature using a filter ratio method. We find that the isothermal temperatures vary from 1.6 to 10 MK. These temperatures are an average weighted toward higher temperature plasma. We determine the mass constraints of eruptive plasmas by assuming simplified geometrical structures of the plasma with isothermal plasma temperatures. This method provides an upper limit to the masses of the observed eruptive plasmas in X-ray passbands since any clumping causes the overestimation of the mass. For the other two events, we assume the ... [READ MORE]

Authors: Jin-Yi Lee, John C. Raymond, Katharine K. Reeves, Yong-Jae Moon, and Kap-Sung Kim
Projects: None

Publication Status: ApJ in press
Last Modified: 2014-11-12 12:36
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A Cross-Comparison of Cotemporal Magnetograms Obtained with MDI/SOHO and SP/ Hinode    

Mei Zhang   Submitted: 2010-01-11 22:41

We compared a set of cotemporal magnetograms of active regions obtained with the Michelson Doppler Imager (MDI) aboard SOHO and the Spectro-Polarimeter (SP) of the Solar Optical Telescope (SOT) on board Hinode. The comparison shows that even with the recent calibration of level-1.8 data, the magnetic flux density derived from the MDI data is still lower than that obtained with SP. The average ratio between current version 2008 MDI level-1.8 data and SP magnetograms is 0.71, and is 0.82 for version 2007 MDI level-1.8 data. The comparison also shows that the most recent version 2008 calibration of MDI level-1.8 data has successfully removed the center-to-limb variation, while version 2007 level-1.8 data did not, as estimated by Ulrich et al.

Authors: Wang, D.; Zhang, M.; Li, H.; Zhang, H. Q.
Projects: None

Publication Status: Solar Physics, 2009, Volume 260, Issue 1, pp.233-244
Last Modified: 2010-01-12 08:51
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Hinode, TRACE, SOHO and ground-based observations of a quiescent prominence    

Pavol Schwartz   Submitted: 2008-09-18 05:28

A quiescent prominence was observed by several instruments on 2007 April 25. The temporal evolution was recorded in H_alpha by Hinode/SOT, in X-rays by Hinode/XRT and in the 195 A channel by TRACE. Moreover, ground-based observatories (GBO) provided calibrated H_alpha intensities. Simultaneous EUV data were also taken by the Hinode/EIS and SOHO/SUMER-CDS spectrometers. Here we have selected the SOT H_alpha image taken at 13:19 UT which nicely shows the prominence fine structure. We compare this image with co-temporal ones taken by XRT and TRACE and show the intensity variations along several cuts parallel to the solar limb. EIS spectra were obtained about half an hour later. Dark prominence structure clearly seen in the TRACE and EIS 195 A images is due to the prominence absorption in ... [READ MORE]

Authors: P. Heinzel, B. Schmieder, F. F?rn?k, P. Schwartz, N. Labrosse, P. Kotr?, U. Anzer, G. Molodij, A. Berlicki, E. E. DeLuca, L. Golub, T. Watanabe, and T. Berger
Projects: None

Publication Status: ApJ, in press, accepted: 2008 June 9
Last Modified: 2008-09-18 08:27
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SDO/AIA and Hinode/EIS Observations of Interaction Between an EUV Wave and Active Region Loops    

Liheng Yang   Submitted: 2013-08-08 19:20

We present detailed analysis of an extreme ultraviolet (EUV) wave and its interaction with active region (AR) loops observed by the Solar Dynamics Observatory/Atmospheric Imaging Assembly and the Hinode EUV Imaging Spectrometer (EIS). This wave was initiated from AR 11261 on 2011 August 4 and propagated at velocities of 430-910 km/s. It was observed to traverse another AR and cross over a filament channel on its path. The EUV wave perturbed neighboring AR loops and excited a disturbance that propagated toward the footpoints of these loops. EIS observations of AR loops revealed that at the time of the wave transit, the original redshift increased by about 3 km/s, while the original blueshift decreased slightly. After the wave transit, these changes were reversed. When the EUV wave arrived ... [READ MORE]

Authors: Liheng Yang, Jun Zhang, Wei Liu, Ting Li and Yuandeng Shen
Projects: None

Publication Status: accepted by ApJ
Last Modified: 2013-08-09 10:07
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Evidence of wave harmonics in a brightened magnetic network observed from Hinode/EIS    

Dr. A.K. Srivastava   Submitted: 2010-04-22 01:52

We study intensity oscillations in the upper chromosphere to search acoustic wave harmonics in a low-atmospheric solar cavity associated with a brightened magnetic network near the south pole of the Sun. We use a wavelet tool to produce power spectrum of He II 256.32 ? intensity oscillation as observed by EUV Imaging Spectrometer (EIS) onboard Hinode spacecraft. We detect a periodicity of 14.33 min with a probability of 99%?100%. Using wavelet filtering and reconstruction techniques, we detect other statistically significant periodicities of 8.51 min and 5.51 min with the probabilities 98% and 97% respectively. These observed periodicities provide the first possible signature of acoustic wave harmonics in a low-atmospheric cavity-canopy system. The ratio of the period of first harmonic ... [READ MORE]

Authors: A.K. Srivastava
Projects: None

Publication Status: New Astronomy, 2010, Vol : 15, pp : 621-627
Last Modified: 2010-04-22 06:46
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Atmospheric Imaging Assembly Response Functions: Solving the Fe VIII Problems with Hinode EIS Bright Point Data    

Joan Schmelz   Submitted: 2013-01-09 10:23

The Atmospheric Imaging Assembly (AIA) onboard the Solar Dynamics Observatory is a state-of-the-art imager with the potential to do unprecedented time-dependent multi-thermal analysis at every pixel on scales short compared to the radiative and conductive cooling times. Recent results, however, have identified missing spectral lines in the CHIANTI atomic physics data base, which is used to construct the instrument response functions. This is not surprising since the wavelength range from 90 ? to 140 ? has rarely been observed with solar spectrometers, and atomic data for many of these ions are simply not available in the literature. We have done differential emission measure analysis using simultaneous AIA and Hinode/EIS observations of six X-ray bright points. Our results not only ... [READ MORE]

Authors: J.T. Schmelz, B.S. Jenkins, J.A. Kimble
Projects: SDO-AIA

Publication Status: Solar Physics, 2013, DOI 10.1007/s11207-012-0208-1
Last Modified: 2013-01-09 10:40
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PERSISTENT DOPPLER SHIFT OSCILLATIONS OBSERVED WITH HINODE/EIS IN THE SOLAR CORONA: SPECTROSCOPIC SIGNATURES OF ALFVENIC WAVES AND RECURRING UPFLOWS    

Hui Tian   Submitted: 2012-12-05 08:12

Using data obtained by the EUV Imaging Spectrometer on board Hinode, we have performed a survey of obvious and persistent (without significant damping) Doppler shift oscillations in the corona. We have found mainly two types of oscillations from February to April in 2007. One type is found at loop footpoint regions, with a dominant period around 10 minutes. They are characterized by coherent behavior of all line parameters (line intensity, Doppler shift, line width, and profile asymmetry), and apparent blueshift and blueward asymmetry throughout almost the entire duration. Such oscillations are likely to be signatures of quasi-periodic upflows (small-scale jets, or coronal counterpart of type-II spicules), which may play an important role in the supply of mass and energy to the ... [READ MORE]

Authors: Hui Tian, Scott W. McIntosh, Tongjiang Wang, Leon Ofman, Bart De Pontieu, Davina E. Innes, and Hardi Peter
Projects: None

Publication Status: The Astrophysical Journal, 759:144 (17pp), 2012 November 10
Last Modified: 2012-12-05 14:04
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Study of the three-dimensional shape and dynamics of coronal loops observed by Hinode/EIS    

Costis Gontikakis   Submitted: 2012-06-01 03:48

We study plasma flows along selected coronal loops in NOAA Active Region 10926, observed on 3 December 2006 with Hinode's EUV Imaging Spectrograph (EIS). From the shape of the loops traced on intensity images and the Doppler shifts measured along their length we compute their three-dimensional (3D) shape and plasma flow velocity using a simple geometrical model. This calculation was performed for loops visible in the Fe VIII 185 Ang., Fe X 184 Ang., Fe XII 195 Ang., Fe XIII 202 Ang., and Fe XV 284 Ang. spectral lines. In most cases the flow is unidirectional from one footpoint to the other but there are also cases of draining motions from the top of the loops to their footpoints. Our results indicate that the same loop may show different flow patterns when observed in different ... [READ MORE]

Authors: P. Syntelis, C. Gontikakis, M.K. Georgoulis, C.E. Alissandrakis, K. Tsinganos
Projects:

Publication Status: In press in Solar Physics
Last Modified: 2012-06-04 08:52
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Transition-region/Coronal Signatures and Magnetic Setting of Sunspot Penumbral Jets: Hinode (SOT/FG), Hi-C, and SDO/AIA Observations    

Sanjiv Tiwari   Submitted: 2016-01-28 09:02

Penumbral microjets (PJs) are transient narrow bright features in the chromosphere of sunspot penumbrae, first characterized by Katsukawa et al. using the Ca ii H-line filter on Hinode's Solar Optical Telescope (SOT). It was proposed that the PJs form as a result of reconnection between two magnetic components of penumbrae (spines and interspines), and that they could contribute to the transition region (TR) and coronal heating above sunspot penumbrae. We propose a modified picture of formation of PJs based on recent results on the internal structure of sunspot penumbral filaments. Using data of a sunspot from Hinode/SOT, High Resolution Coronal Imager, and different passbands of the Atmospheric Imaging Assembly (AIA) on board the Solar Dynamics Observatory, we examine whether PJs have ... [READ MORE]

Authors: Tiwari, Sanjiv K.; Moore, Ronald L.; Winebarger, Amy R.; Alpert, Shane E.
Projects: Hi-C

Publication Status: published in ApJ, Jan 14, 2016
Last Modified: 2016-02-03 09:19
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Observations from Hinode/EIS of intensity oscillations above a bright point: signature of the leakage of acoustic oscillations in the inner corona    

Dr. A.K. Srivastava   Submitted: 2010-06-04 04:43

We study the intensity oscillations in the upper chromosphere/transition region (TR) and corona, above a bright point (BP) in the solar atmosphere. We analyse the time series of HeII 256 ?, FeXII 195 ? and FeXV 284 ?, observed in a 40-arcsec slot close to the centre of the Sun above the BP by the extreme ultraviolet (EUV) imaging spectrometer (EIS) on board Hinode. Using standard wavelet and periodogram tools, we produce power spectra of intensity oscillations. In the HeII 256.32 ? and FeXII 195.12 ? EUV light curves, we detect intensity oscillations of the periods ~ 263 +/- 80 s and ~ 241 +/- 60 s, respectively, with a probability >95 per cent in wavelets, which are also consistent with their periodograms. This provides the most likely signature of the propagation of acoustic ... [READ MORE]

Authors: Srivastava, A. K.; Dwivedi, B. N.
Projects: None

Publication Status: MNRAS
Last Modified: 2010-06-04 07:44
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Nonlinear force-free field extrapolation of the coronal magnetic field using the data obtained by the Hinode satellite    

Han He   Submitted: 2011-12-05 20:15

The Hinode satellite can obtain high-quality photospheric vector magnetograms of solar active regions and the simultaneous coronal loop images in soft X-ray and extreme ultraviolet (EUV) bands. In this paper, we continue the work of He and Wang (2008) and apply the newly developed upward boundary integration computational scheme for the nonlinear force-free field (NLFFF) extrapolation of the coronal magnetic field to the photospheric vector magnetograms acquired by the Spectro-Polarimeter of the Solar Optical Telescope aboard Hinode. Three time series vector magnetograms of the same solar active region, NOAA 10930, are selected for the NLFFF extrapolations, which were observed within the time interval of 26 h during 10-11 December 2006 when the active region crossed the central area of ... [READ MORE]

Authors: Han He, Huaning Wang, Yihua Yan
Projects: None

Publication Status: Journal of Geophysical Research - Space Physics (published)
Last Modified: 2011-12-05 20:18
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THE NASCENT FAST SOLAR WIND OBSERVED BY THE EUV IMAGING SPECTROMETER ON BOARD HINODE    

Hui Tian   Submitted: 2012-12-05 08:26

The origin of the solar wind is one of the most important unresolved problems in space and solar physics. We report here the first spectroscopic signatures of the nascent fast solar wind on the basis of observations made by the EUV Imaging Spectrometer on Hinode in a polar coronal hole in which patches of blueshift are clearly present on Dopplergrams of coronal emission lines with a formation temperature of lg(T/K) > 5.8. The corresponding upflow is associated with open field lines in the coronal hole and seems to start in the solar transition region and becomes more prominent with increasing temperature. This temperature-dependent plasma outflow is interpreted as evidence of the nascent fast solar wind in the polar coronal hole. The patches with significant upflows are ... [READ MORE]

Authors: Hui Tian, Chuanyi Tu, Eckart Marsch, Jiansen He, and Suguru Kamio
Projects: None

Publication Status: The Astrophysical Journal Letters, 709:L88?L93, 2010 January 20
Last Modified: 2012-12-05 14:05
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Hinode 7: Conference Summary and Future Suggestions    

Eric R Priest   Submitted: 2014-05-15 03:31

This conclusion to the meeting attempts to summarise what we have learnt during the conference (mainly from the review talks) about new observations from Hinode and about theories stimulated by them. Suggestions for future study are also offered.

Authors: Priest, ER
Projects: None

Publication Status: In press
Last Modified: 2014-05-15 15:19
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Signatures of Interchange Reconnection: STEREO, ACE and Hinode Observations Combined    

Deborah Baker   Submitted: 2009-09-30 07:55

Combining STEREO, ACE and Hinode observations has presented an opportunity to follow a filament eruption and coronal mass ejection (CME) on the 17th of October 2007 from an active region (AR) inside a coronal hole (CH) into the heliosphere. This particular combination of `open' and closed magnetic topologies provides an ideal scenario for interchange reconnection to take place. With Hinode and STEREO data we were able to identify the emergence time and type of structure seen in the in-situ data four days later. On the 21st, ACE observed in-situ the passage of an ICME with `open' magnetic topology. The magnetic field configuration of the source, a mature AR located inside an equatorial CH, has important implications for the solar and interplanetary signatures of the eruption. We ... [READ MORE]

Authors: D. Baker, A. P. Rouillard, L. van Driel-Gesztelyi, P. Demoulin, L. K. Harra, B. Lavraud, J. A. Davies, A. Opitz, J. G. Luhmann, J. A. Sauvaud, A. B. Galvin
Projects: STEREO

Publication Status: Annales Geophysicae (Accepted)
Last Modified: 2009-09-30 08:09
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Solar Coronal Loops Resolved by Hinode and SDO    

David Brooks   Submitted: 2012-06-06 20:29

Despite decades of studying the Sun, the coronal heating problem remains unsolved. One fundamental issue is that we do not know the spatial scale of the coronal heating mechanism. At a spatial resolution of 1000 km or more it is likely that most observations represent superpositions of multiple unresolved structures. In this letter, we use a combination of spectroscopic data from the Hinode EUV Imaging Spectrometer (EIS) and high resolution images from the Atmospheric Imaging Assembly (AIA) on the Solar Dynamics Observatory to determine the spatial scales of coronal loops. We use density measurements to construct multi-thread models of the observed loops and confirm these models using the higher spatial resolution imaging data. The results allow us to set constraints on the number of ... [READ MORE]

Authors: David H. Brooks, Harry P. Warren, Ignacio Ugarte-Urra
Projects: None

Publication Status: To be published in ApJ Letters
Last Modified: 2012-06-07 09:21
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On active region loops: Hinode/EIS observations    

Durgesh Tripathi   Submitted: 2008-12-31 06:15

We have carried out a study of active region loops using observations from the Extreme-ultraviolet Imaging Spectrometer (EIS) on board Hinode using 1~arcsec~raster data for an active region observed on May 19, 2007. We find that active region structures which are clearly discernible in cooler lines ($approx$~1MK) become 'fuzzy' at higher temperatures ($approx$~2MK). The active region was comprised of red-shifted emissions (downflows) in the core and blue-shifted emissions (upflows) at the boundary. The flow velocities estimated in two regions located near the foot points of coronal loop showed red-shifted emission at transition region temperature and blue shifted emission at coronal temperature. The upflow speed in these regions increased with temperature. For more detailed ... [READ MORE]

Authors: D. Tripathi, H.E.Mason, B. N. Dwivedi, G. Del Zanna, P.R. Young
Projects: None

Publication Status: Accepted for Publication in ApJ
Last Modified: 2008-12-31 07:13
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Observation of intensity oscillations above X-ray bright points from the Hinode/XRT: signature of magnetohydrodynamic oscillations in the solar corona    

Dr. A.K. Srivastava   Submitted: 2011-06-22 02:54

We analyse the temporal image data of the quiet Sun observed by the X-ray Telescope (XRT) onboard the Hinode spacecraft and Al-poly filter on 2007 March 31. We choose these temporal image data of ∼30 s cadence from 11:34:48 ut to 14:19:35 ut to study intensity oscillations above selected X-ray bright points (XBPs) with an exposure time 8.193 s of each XRT image. Using the Fourier filtering method, we reconstruct X-ray light curves for the periods outside the cone-of-influence (COI) of their power spectrum. Using the standard wavelet software, we derive the power spectra of the reconstructed light curves which are generated by filtering the original X-ray time-series at the Fourier scale (54.55 min) ... [READ MORE]


Authors: Kumar, Mukul; Srivastava, A. K.; Dwivedi, B. N.
Projects: None

Publication Status: Published in MNRAS
Last Modified: 2011-06-22 12:24
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Direct Observations of Magnetic Reconnection Outflow and CME Triggering in a Small Erupting Solar Prominence   

Kathy Reeves   Submitted: 2015-05-28 09:50

We examine a small prominence eruption that occurred on 2014 May 1 at 01:35 UT and was observed by the {\it Interface Region Imaging Spectrometer} ({\it IRIS}) and the Atmospheric Imaging Assembly (AIA) on the {\it Solar Dynamics Observatory} ({\it SDO}). Pre- and post-eruption images were taken by the X-Ray Telescope (XRT) on {\it Hinode}. Pre-eruption, a dome-like structure exists above the prominence, as demarcated by coronal rain. As the eruption progresses, we find evidence for reconnection between the prominence magnetic field and the overlying field. Fast flows are seen in AIA and {\it IRIS}, indicating reconnection outflows. Plane-of-sky flows of ~300 km s$^{-1}$ are observed in the AIA 171 A channel along a potentially reconnected field line. {\it IRIS} detects ... [READ MORE]

Authors: Katharine K. Reeves, Patrick I. McCauley and Hui Tian
Projects: Hinode/XRT,IRIS,SDO-AIA

Publication Status: Accepted in ApJL
Last Modified: 2015-05-30 04:31
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The Formation and Magnetic Structures of Active-region Filaments Observed by NVST, SDO, and Hinode   

Xiaoli Yan   Submitted: 2015-08-25 17:30

To better understand the properties of solar active-region filaments, we present a detailed study on the formation and magnetic structures of two active-region filaments in active region NOAA 11884 during a period of four days. It is found that the shearing motion of the opposite magnetic polarities and the rotation of the small sunspots with negative polarity play an important role in the formation of two active-region filaments. During the formation of these two active-region filaments, one foot of the filaments was rooted in a small sunspot with negative polarity. The small sunspot rotated not only around another small sunspot with negative polarity, but also around the center of its umbra. By analyzing the nonlinear force-free field extrapolation using the vector magnetic fields in ... [READ MORE]

Authors: X.L. Yan, Z.K. Xue, G.M. Pan, J.C. Wang, Y.Y. Xiang, D.F. Kong, and L.H. Yang
Projects: SDO-AIA,SDO-HMI

Publication Status: Published in the Astrophysical Journal Supplement Series
Last Modified: 2015-08-26 13:13
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Subject will be restored when possible   

John Mariska   Submitted: 2008-06-03 04:55

Damped Doppler shift oscillations have been observed in emission lines from ions formed at flare temperatures with the Solar Ultraviolet Measurements of Emitted Radiation spectrometer on the Solar and Heliospheric Observatory and with the Bragg Crystal Spectrometer on Yohkoh. This Letter reports the detection of low-amplitude damped oscillations in coronal emission lines formed at much lower temperatures observed with the EUV Imaging Spectrometer on the Hinode satellite. The oscillations have an amplitude of about 2 km/s, and a period of around 35 min. The decay times show some evidence for a temperature dependence with the lowest temperature of formation emission line (Fe XII 195.12 Angstroms) exhibiting a decay time of about 43 min, while the highest temperature of formation emission ... [READ MORE]

Authors: Mariska, J.T., Warren, H.P., Williams, D.R., Watanabe, T.
Projects: Hinode/EIS

Publication Status: ApJ Letters in press
Last Modified: 2008-09-23 21:01
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Subject will be restored when possible   

Yihua Yan   Submitted: 2007-10-08 04:16

On 2006 December 13 during the solar minimum, the superactive region NOAA 10930 at S05W33 disk location produced an X3.4/4B flare at 02:40 UT. Fine structures were observed in the radio spectra, which include spikes, reverse slope type III bursts, type U burst, V-shaped burst, pulsations, zebra patterns and firstly-discovered sub-second spiky zebra-like structures, superimposed in the 2.6 -- 3.8 GHz type IV bursts. The radio fine structures during the impulsive phase of the flare may be closely associated with coronal structures during the magnetic reconnection process as revealed by {Hinode} soft X-ray images. Thus these microwave fine structure observations may provide very useful diagnostics in the primary energy release sites when they occur in the impulsive flare phase. For this ... [READ MORE]

Authors: Yihua Yan, Jing Huang, Bin Chen, Takashi Sakurai
Projects: Hinode,RHESSI,SoHO-MDI

Publication Status: PASJ Vol.59, 2007 (Hinode special issue, in press)
Last Modified: 2007-10-08 17:14
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Characteristic Dependence of Umbral Dots on their Magnetic Structure   

Hiroko Watanabe   Submitted: 2009-07-15 23:25

Umbral dots (UDs) were observed in a stable sunspot in NOAA 10944 by the Hinode Solar Optical Telescope on 2007 March 1. The observation program consisted of blue continuum images and spectropolarimetric profiles of Fe I 630 nm line. An automatic detection algorithm for UDs was applied to the 2-hour continuous blue continuum images, and using the obtained data, the lifetime, size, and proper motion of UDs were calculated. The magnetic structure of the sunspot was derived through the inversion of the spectropolarimetric profiles. We calculated the correlations between UD's parameters (size, lifetime, occurrence rate, proper motion) and magnetic fields (field strength, inclination, azimuth), and obtained the following results: (1) Both the lifetime and size of UDs are almost ... [READ MORE]

Authors: Hiroko Watanabe, Reizaburo Kitai, Kiyoshi Ichimoto
Projects: Hinode/SOT

Publication Status: accepted for publication in ApJ
Last Modified: 2009-07-16 08:34
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Observations and Nonlinear Force-Free Field Modeling of Active Region 10953   

Yingna Su   Submitted: 2008-09-22 13:45

We present multi-wavelength observations of a simple bipolar active region (NOAA 10953), which produced several small flares (mostly B class and one C8.5 class) and filament activations from April 30 to May 3 in 2007. We also explore non-linear force free field (NLFFF) modeling of this region prior to the C8.5 flare on May 2, using magnetograph data from SOHO/MDI and Hinode/SOT. A series of NLFFF models are constructed using the flux-rope insertion method. By comparing the modeled field lines with multiple X-ray loops observed by Hinode/XRT, we find that the axial flux of the flux rope in the best-fit models is 7e20 Mx, while the poloidal flux has a wider range of (0.1-10)e10 Mx/cm. The axial flux in the best-fit model is well below the upper limit (~15e20 Mx) for stable force-free ... [READ MORE]

Authors: Yingna Su, Adriaan van Ballegooijen, Bruce W. Lites, Edward E. Deluca, Leon Golub, Paolo C. Grigis, Guangli Huang, and Haisheng Ji
Projects: Hinode/XRT

Publication Status: Astrophysical Journal, 2009, 691, 105-114.
Last Modified: 2009-02-05 08:39
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The multi-thermal emission in solar active regions   

Giulio Del Zanna   Submitted: 2013-07-10 07:06

We present simultaneous SDO AIA and Hinode EIS observations of the hot cores of active regions (ARs) and assess the dominant contributions to the AIA EUV bands, extending our previous work. We find good agreement between SDO AIA, EVE and EIS observations, using our new EIS calibration and the latest EVE v.3 data. We find that all the AIA bands are multi-thermal, with the exception of the 171 and 335 A, and provide ways to roughly estimate the main contributions directly from the AIA data. We present and discuss new atomic data for the AIA bands, showing that they are now sufficiently complete to obtain temperature information in the cores of ARs, with the exception of the 211 A band. We found that the newly identified Fe XIV 93.61 A line is the ... [READ MORE]

Authors: G. Del Zanna
Projects: Hinode/EIS,SDO-AIA,SDO-EVE,SoHO-CDS

Publication Status: Accepted for publication in A&A
Last Modified: 2013-07-10 13:40
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Subject will be restored when possible   

Yihua Yan   Submitted: 2007-10-08 04:16

On 2006 December 13 during the solar minimum, the superactive region NOAA 10930 at S05W33 disk location produced an X3.4/4B flare at 02:40 UT. Fine structures were observed in the radio spectra, which include spikes, reverse slope type III bursts, type U burst, V-shaped burst, pulsations, zebra patterns and firstly-discovered sub-second spiky zebra-like structures, superimposed in the 2.6 -- 3.8 GHz type IV bursts. The radio fine structures during the impulsive phase of the flare may be closely associated with coronal structures during the magnetic reconnection process as revealed by {Hinode} soft X-ray images. Thus these microwave fine structure observations may provide very useful diagnostics in the primary energy release sites when they occur in the impulsive flare phase. For this ... [READ MORE]

Authors: Yihua Yan, Jing Huang, Bin Chen, Takashi Sakurai
Projects: Hinode,RHESSI,SoHO-MDI

Publication Status: PASJ Vol.59, 2007 (Hinode issue)
Last Modified: 2007-10-08 07:11
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Outflows at the Edges of an Active Region in a Coronal Hole: A Signature of Active Region Expansion?   

Deborah Baker   Submitted: 2009-12-07 03:14

Outflows of plasma at the edges of active regions surrounded by quiet Sun are now a common observation with the Hinode satellite. While there is observational evidence to suggest that the outflows are originating in the magnetic field surrounding the active regions, there is no conclusive evidence that reveals how they are driven. Motivated by observations of outflows at the periphery of a mature active region embedded in a coronal hole, we have used a three-dimensional simulation to emulate the active region?s development in order to investigate the origin and driver of these outflows. We find outflows are accelerated from a site in the coronal hole magnetic field immediately surrounding the active region and are channelled along the coronal hole field as they rise through the ... [READ MORE]

Authors: M.J. Murray, D. Baker, L. van Driel-Gesztelyi, J. Sun
Projects: Hinode/EIS

Publication Status: Accepted by Solar Physics
Last Modified: 2009-12-07 10:35
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Interaction and Eruption of Two Filaments Observed by Hinode, SOHO, and STEREO   

Ying Li   Submitted: 2011-11-18 02:30

This abstract was corrupted following database problems and is being recovered. It will be restored as quickly as possible. Any questions, please send them to Alisdair. Sorry for any incovenience.


Authors: Y. Li and M. D. Ding
Projects:

Publication Status: Accepted for publication in RAA
Last Modified: 2011-11-19 00:57
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FORMATION OF TORUS-UNSTABLE FLUX ROPES AND ELECTRIC CURRENTS IN ERUPTING SIGMOIDS   

Guillaume Aulanier   Submitted: 2009-11-06 05:48

We analyze the physical mechanisms that form a three-dimensional coronal flux rope and later cause its eruption. This is achieved by a zero-beta MHD simulation of an initially potential, asymmetric bipolar field, which evolves by means of simultaneous slow magnetic field diffusion and sub-Alfvenic, line-tied shearing motions in the photosphere. As in similar models, flux-cancellation driven photospheric reconnection in a bald-patch separatrix transforms the sheared arcades into a slowly rising and stable flux rope. A bifurcation from a bald-patch to a quasi-separatrix layer (QSL) topology occurs later on in the evolution, while the flux rope keeps growing and slowly rising, now due to shear-driven coronal slip-running reconnection, which is of tether-cutting type and takes place in ... [READ MORE]

Authors: G. Aulanier, T. Torok, P. Demoulin, E.E. DeLuca
Projects: Hinode/XRT

Publication Status: in press
Last Modified: 2009-11-06 09:59
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Subject will be restored when possible   

Alexander Kosovichev   Submitted: 2007-10-10 14:35

Observations of a large solar flare of December 13, 2006, using Solar Optical Telescope (SOT) on Hinode spacecraft revealed high-frequency oscillations excited by the flare in the sunspot chromosphere. These oscillations are observed in the region of strong magnetic field of the sunspot umbra, and may provide a new diagnostic tool for probing the structure of sunspots and understanding physical processes in solar flares.

Authors: A.G. Kosovichev and T. Sekii
Projects: Hinode

Publication Status: ApJL (in press)
Last Modified: 2007-10-11 09:41
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The quiet Sun average Doppler shift of coronal lines up to 2~MK   

Luca Teriaca   Submitted: 2011-09-22 03:12

The average Doppler shift shown by spectral lines formed from the chromosphere to the corona reveals important information on the mass and energy balance of the solar atmosphere, providing an important observational constraint to any models of the solar corona. Previous spectroscopic observations of vacuum ultra-violet (VUV) lines have revealed a persistent average wavelength shift of lines formed at temperatures up to 1 MK. At higher temperatures, the behaviour is still essentially unknown. Here we analyse combined SUMER/SoHO and EIS/Hinode observations of the quiet Sun around disk centre to determine, for the first time, the average Doppler shift of several spectral lines formed between 1 and 2 MK, where the largest part of the quiet coronal emission is formed. The measurements are ... [READ MORE]

Authors: N. Dadashi, L. Teriaca, S.K. Solanki
Projects: Hinode/EIS,SoHO-SUMER

Publication Status: Astronomy and Astrophysics (in press)
Last Modified: 2011-09-22 13:03
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Revision of Solar Spicule Classification   

Yuzong Zhang   Submitted: 2012-02-20 22:11

Solar spicules are the fundamental magnetic structures in the chromosphere and considered to play a key role in channeling the chromosphere and corona. Recently, it was suggested by De Pontieu et al. that there were two types of spicules with very different dynamic properties, which were detected by space- time plot technique in the Ca II H line (3968A) wavelength from Hinode/SOT observations. 'Type I' spicule, with a 3-7 minute lifetime, undergoes a cycle of upward and downward motion; in contrast, 'Type II' spicule fades away within dozens of seconds, without descending phase. We are motivated by the fact that for a spicule with complicated 3D motion, the space-time plot, which is made through a slit on a fixed position, could not match the spicule behavior all the time and might lose ... [READ MORE]

Authors: Y. Z. Zhang, K. Shibata, J. X. Wang, X. J. Mao, T. Matsumoto, Y. Liu, and J. T. Su
Projects: Hinode/SOT

Publication Status: Accepted by ApJ on Feb 18, 2012
Last Modified: 2012-02-21 10:24
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Extreme Ultra-Violet Spectroscopy of the Flaring Solar Chromosphere   

Ryan Milligan   Submitted: 2015-01-12 10:47

The extreme ultraviolet portion of the solar spectrum contains a wealth of diagnostic tools for probing the lower solar atmosphere in response to an injection of energy, particularly during the impulsive phase of solar flares. These include temperature and density sensitive line ratios, Doppler shifted emission lines and nonthermal broadening, abundance measurements, Differential Emission Measure profiles, and continuum temperatures and energetics, among others. In this paper I shall review some of the advances made in recent years using these techniques, focusing primarily on studies that have utilized data from Hinode/EIS and SDO/EVE, while also providing some historical background and a summary of future spectroscopic instrumentation.

Authors: Ryan O. Milligan
Projects: Hinode/EIS,SDO-EVE,SoHO-CDS,SoHO-SUMER

Publication Status: Submitted to Solar Physics for Topical Issue on Solar and Stellar Flares
Last Modified: 2015-01-12 11:58
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Modeling and Interpreting the Effects of Spatial Resolution on Solar Magnetic Field Maps   

K.D. Leka   Submitted: 2011-10-18 21:45

Different methods for simulating the effects of spatial resolution on magnetic field maps are compared, including those commonly used for inter-instrument comparisons. The investigation first uses synthetic data, and the results are confirmed with {it Hinode}/SpectroPolarimeter data. Four methods are examined, one which manipulates the Stokes spectra to simulate spatial-resolution degradation, and three 'post-facto' methods where the magnetic field maps are manipulated directly. Throughout, statistical comparisons of the degraded maps with the originals serve to quantify the outcomes. Overall, we find that areas with inferred magnetic fill fractions close to unity may be insensitive to optical spatial resolution; areas of sub-unity fill fractions are very sensitive. Trends with ... [READ MORE]

Authors: K.D. Leka, Graham Barnes
Projects: Hinode/SOT

Publication Status: Solar Physics, in press. doi: 10.1007/s11207-011-9821-7
Last Modified: 2011-10-19 09:21
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Ca II K Spectral Study of an Emerging Flux Region using Domeless Solar Telescope in Hida Observatory   

Kenichi Otsuji   Submitted: 2010-05-12 18:10

A cooperative observation with Hida observatory and Hinode satellite was performed on an emerging flux region. The successive Ca II K spectro-heliograms of the emerging flux region were taken by the Domeless Solar Telescope of Hida observatory. Hinode observed the emerging flux region with Ca II H and Fe I Stokes IQUV filtergrams. In this study, detailed dynamics and temporal evolution of the magnetic flux emergence was studied observationally. The event was first detected in the photospheric magnetic field signals. 3 minutes later, the horizontal expansion of the dark area was detected. And then, 7 minutes later than the horizontal expansion, the emerging loops were detected with the maximal rise speed of 2.1 km/s at chromospheric heights. The observed dynamics of emerging magnetic flux ... [READ MORE]

Authors: Kenichi Otsuji, Reizaburo Kitai, Takuma Matsumoto, Kiyoshi Ichimoto, Satoru Ueno, Shin'ichi Nagata, Hiroaki Isobe, Kazunari Shibata
Projects: Hinode/SOT

Publication Status: Accepted
Last Modified: 2010-05-13 07:17
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Magnetic Non-Potentiality of Solar Active Regions and Peak X-Ray Flux of the Associated Flares   

Sanjiv Kumar Tiwari   Submitted: 2010-07-29 08:04

Predicting the severity of the solar eruptive phenomena like flares and Coronal Mass Ejections (CMEs) remains a great challenge despite concerted efforts for several decades. The advent of high quality vector magnetograms obtained from Hinode (SOT/SP) has increased the possibility of meeting this challenge. In particular, the Spatially Averaged Signed Shear Angle (SASSA) seems to be an unique parameter to quantify the non-potentiality of the active regions. We demonstrate the usefulness of SASSA for predicting the flare severity. For this purpose we present case studies of the evolution of magnetic non-potentiality using 115 vector magnetograms of four active regions namely ARs NOAA 10930, 10960, 10961 and 10963 during December 08$-$15, 2006, June 03$-$10, 2007, June 28$-$July 5, 2007 ... [READ MORE]

Authors: Sanjiv Kumar Tiwari, P. Venkatakrishnan, and Sanjay Gosain
Projects: Hinode/SOT

Publication Status: Accepted for publication in the Astrophysical Journal
Last Modified: 2010-08-01 03:22
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Active region transition region loop populations and their relationship to the corona   

Ignacio Ugarte-Urra   Submitted: 2009-01-09 06:52

The relationships among coronal loop structures at different temperatures is not settled. Previous studies have suggested that coronal loops in the core of an active region are not seen cooling through lower temperatures and therefore are steadily heated. If loops were cooling, the transition region would be an ideal temperature regime to look for a signature of their evolution. The Extreme-ultraviolet Imaging Spectrometer (EIS) on Hinode provides monochromatic images of the solar transition region and corona at an unprecedented cadence and spatial resolution, making it an ideal instrument to shed light on this issue. Analysis of observations of active region 10978 taken in 2007 December 8 -- 19 indicates that there are two dominant loop populations in the active region: core ... [READ MORE]

Authors: Ignacio Ugarte-Urra, Harry P. Warren, David H. Brooks
Projects: Hinode/EIS

Publication Status: ApJ, in press
Last Modified: 2009-01-09 09:37
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Determining heating time scales in solar active region cores from AIA/SDO Fe XVIII images   

Ignacio Ugarte-Urra   Submitted: 2014-01-15 14:23

We present a study of the frequency of transient brightenings in the core of solar active regions as observed in the Fe XVIII line component of AIA/SDO 94 A filter images. The Fe XVIII emission is isolated using an empirical correction to remove the contribution of ''warm'' emission to this channel. Comparing with simultaneous observations from EIS/Hinode, we find that the variability observed in Fe XVIII is strongly correlated with the emission from lines formed at similar temperatures. We examine the evolution of loops in the cores of active regions at various stages of evolution. Using a newly developed event detection algorithm we characterize the distribution of event frequency, duration, and magnitude in these active regions. These distributions are similar for regions of similar ... [READ MORE]

Authors: Ignacio Ugarte-Urra, Harry P. Warren
Projects: Hinode/EIS,SDO-AIA

Publication Status: ApJ (in press)
Last Modified: 2014-01-18 17:12
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Subject will be restored when possible   

Durgesh Tripathi   Submitted: 2007-10-03 04:30

The Extreme-ultraviolet Imaging Spectrometer (EIS) on board Hinode provides an excellent opportunity to study the physical plasma parameters in spatially resolved coronal features. In this paper we present the density structure in an active region at many different temperatures. The active region was rastered on May 01, 2007 with the 2 arcsec slit. We find that the electron density is highest in the core of the active region where it exceeds Log (Ne)=10.5.

Authors: D. Tripathi, H. E. Mason, P. R. Young, C. Chifor, G. Del Zanna
Projects: Hinode

Publication Status: Submitted for publication
Last Modified: 2007-10-03 07:45
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The Evolution of Sunspot Magnetic Fields Associated with a Solar Flare   

Sophie A. Murray   Submitted: 2011-05-11 02:27

Solar flares occur due to the sudden release of energy stored in active-region magnetic fields. To date, the pre-cursors to flaring are still not fully understood, although there is evidence that flaring is related to changes in the topology or complexity of an active region's magnetic field. Here, the evolution of the magnetic field in active region NOAA 10953 was examined using Hinode/SOT-SP data, over a period of 12 hours leading up to and after a GOES B1.0 flare. A number of magnetic-field properties and low-order aspects of magnetic-field topology were extracted from two flux regions that exhibited increased Ca II H emission during the flare. Pre-flare increases in vertical field strength, vertical current density, and inclination angle of ~ 8degrees towards the vertical were ... [READ MORE]

Authors: Sophie A. Murray, D. Shaun Bloomfield, Peter T. Gallagher
Projects: Hinode/SOT

Publication Status: Solar Physics (accepted)
Last Modified: 2011-05-11 09:12
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Dipolar Evolution in a Coronal Hole Region   

Shuhong Yang   Submitted: 2009-08-04 21:01

Using observations from the SOHO, STEREO and Hinode, we investigate magnetic field evolution in an equatorial coronal hole region. Two dipoles emerge one by one. The negative element of the first dipole disappears due to the interaction with the positive element of the second dipole. During this process, a jet and a plasma eruption are observed. The opposite polarities of the second dipole separate at first, and then cancel with each other, which is first reported in a coronal hole. With the reduction of unsigned magnetic flux of the second dipole from 9.8?10^20 Mx to 3.0?10^20 Mx in two days, 171 ? brightness decreases by 75% and coronal loops shrink obviously. At the cancellation sites, the transverse fields are strong and point directly from the positive elements to the negative ones, ... [READ MORE]

Authors: Shuhong Yang, Jun Zhang, and Juan Manuel Borrero
Projects: Hinode/SOT,SoHO-EIT,SoHO-MDI,STEREO

Publication Status: accepted by ApJ
Last Modified: 2009-08-05 14:22
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Subject will be restored when possible   

Peter Young   Submitted: 2007-08-31 04:19

Two types of active region feature prominent at transition region temperatures are identified in Hinode/EIS data of AR 10938 taken on 2007 January 20. The footpoints of 1 MK TRACE loops are shown to emit strongly in emission lines formed at log T=5.4-5.8, allowing the temperature increase along the footpoints to be clearly seen. A density diagnostic of Mg VII yields the density in the footpoints, with one loop showing a decrease from 3x10^9 cm^-3 at the base to 1.5x10^9 cm^-3 at a projected height of 20 Mm. The second feature is a compact active region transition region brightening which is particularly intense in O V emission (log T=5.4) but also has a signature at temperatures up to log T=6.3. The Mg VII diagnostic gives a density of 4x10^10 cm^-3, and emission lines of Mg VI and Mg VII ... [READ MORE]

Authors: P. R. Young, G. Del Zanna, H. E. Mason, G. A. Doschek, J. L. Culhane, H. Hara
Projects: Hinode

Publication Status: Accepted for PASJ Hinode special issue
Last Modified: 2007-08-31 18:06
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Fan-spine topology formation through two-step reconnection driven by twisted flux emergence   

Tibor Toeroek   Submitted: 2009-09-14 08:55

We address the formation of 3D nullpoint topologies in the solar corona by combining Hinode/XRT observations of a small dynamic limb event, which occurred beside a non-erupting prominence cavity, with a 3D zero-beta MHD simulation. To this end, we model the boundary-driven kinematic emergence of a compact, intense, and uniformly twisted flux tube into a potential field arcade that overlies a weakly twisted coronal flux rope. The expansion of the emerging flux in the corona gives rise to the formation of a nullpoint at the interface of the emerging and the pre-existing fields. We unveil a two-step reconnection process at the nullpoint that eventually yields the formation of a broad 3D fan-spine configuration above the emerging bipole. The first reconnection involves emerging fields and a ... [READ MORE]

Authors: T. Toeroek, G. Aulanier, B. Schmieder, K.K. Reeves, L. Golub
Projects: Hinode/XRT

Publication Status: ApJ (in press)
Last Modified: 2009-09-14 09:33
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Comparing UV/EUV line parameters and magnetic field in a quiescent prominence with tornadoes   

Peter Levens   Submitted: 2017-08-21 08:45

Context. Understanding the close relationship between the plasma and the magnetic field is important to describe and explain the observed complex dynamics of solar prominences. Aims. We determine if a close relationship between plasma and magnetic field parameters measured in a well-observed solar prominence with high spatial resolution can be found. Methods. We select a prominence observed on 15 July 2014 from space (IRIS, Hinode, SDO) and from the ground (THEMIS). We perform a robust co-alignment of the data sets using a 2D cross-correlation technique. We derive the magnetic field parameters from spectropolarimetric measurements of the He I D3 line taken by THEMIS. Line ratios and line-of-sight velocities from the Mg II h and k lines observed by IRIS are compared with magnetic field ... [READ MORE]

Authors: P. J. Levens, N. Labrosse, B. Schmieder, A. L?pez Ariste, L. Fletcher
Projects: Hinode/EIS,Hinode/SOT,IRIS,THEMIS/MTR

Publication Status: A&A (accepted)
Last Modified: 2017-08-23 12:50
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Subject will be restored when possible   

Kathy Reeves   Submitted: 2007-11-08 15:51

The X-Ray Telescope on Hinode has observed individual loops of plasma moving downward in a manner that is consistent with field line shrinkage in the aftermath of reconnection at higher altitudes. A on-disk B3.8 flare observed on May 02, 2007, has loops that clearly change in shape from cusp-shaped to more rounded. In addition, bright loops are observed that decrease in altitude with a speed of approximately 5 km/s and fainter, higher loop structures shrink with a velocity of 48 km/s. A C2.1 flare observed on December 17, 2006, also has loops that change shape. Many bright features are seen to be moving downward in this event, and we estimate their speed to be around 2-4 km/s. We measure the shrinkage in both of these events, and find that it is 17-27%, which is consistent with ... [READ MORE]

Authors: Reeves, K. K., Seaton, D. B. and Forbes, T. G.
Projects: Hinode

Publication Status: ApJ (in press)
Last Modified: 2007-11-09 07:53
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Propagating disturbances in coronal loops: flows or waves?   

Tongjiang Wang   Submitted: 2011-02-08 10:54

Quasi-periodic intensity disturbances propagating upward along the coronal structure have been extensively studied using EUV imaging observations from SOHO/EIT and TRACE. They were interpreted as either slow mode magnetoacoustic waves or intermittent upflows. In this study we aim at demonstrating that time series of spectroscopic observations are critical to solve this puzzle. Propagating intensity and Doppler shift disturbances in fanlike coronal loops are analyzed in multiple wavelengths using the sit-and-stare observations from Hinode/EIS. We find that the disturbances did not cause the blue-wing asymmetry of spectral profiles in the warm (~1.5 MK) coronal lines. The estimated small line-of-sight velocities also did not support the intermittent upflow interpretation. In the hot (~2 ... [READ MORE]

Authors: T.J. Wang, L. Ofman, and J. M. Davila
Projects: Hinode/EIS

Publication Status: Hinode 4 meeting (2010), submitted (ASP Conference Series)
Last Modified: 2011-02-09 09:16
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Propagating Waves Transverse to the Magnetic Field in a Solar Prominence   

Manuel Luna   Submitted: 2013-09-09 04:06

We report an unusual set of observations of waves in a large prominence pillar which consist of pulses propagating perpendicular to the prominence magnetic field. We observe a huge quiescent prominence with the Solar Dynamics Observatory (SDO) Atmospheric Imaging Assembly (AIA) in EUV on 2012 October 10 and only a part of it, the pillar, which is a foot or barb of the prominence, with the Hinode Solar Optical Telescope (SOT) (in Ca II and Hα lines), Sac Peak (in Hα, Hβ and Na-D3 lines), THEMIS (?T?lescope H?liographique pour l? Etude du Magn?tisme et des Instabilit?s Solaires?) with the MTR (MulTi-Raies) spectropolarimeter (in He D3 line). The THEMIS/MTR data indicates that the magnetic field in the pillar is essentially horizontal and the observations in the ... [READ MORE]

Authors: B. Schmieder, T.A. Kucera, K. Knizhnik, M. Luna, A. Lopez-Ariste, and D.Toot
Projects: Hinode/SOT,SDO-AIA,THEMIS/MTR

Publication Status: Accepted for publication in The Astrophysical Journal
Last Modified: 2013-09-09 10:12
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Subject will be restored when possible   

Karel Schrijver   Submitted: 2007-11-30 15:20

Solar flares and coronal mass ejections are associated with rapid changes in field connectivity and powered by the partial dissipation of electrical currents in the solar atmosphere. A critical unanswered question is whether the currents involved are induced by the motion of pre-existing atmospheric magnetic flux subject to surface plasma flows, or whether these currents are associated with the emergence of flux from within the solar convective zone. We address this problem by applying state-of-the-art nonlinear force-free field (NLFFF) modeling to the highest resolution and quality vector-magnetographic data observed by the recently launched Hinode satellite on NOAA Active Region 10930 around the time of a powerful X3.4 flare. We compute 14 NLFFF models with 4 different codes ... [READ MORE]

Authors: C.J. Schrijver, M.L. DeRosa, T. Metcalf, G. Barnes, B. Lites, T. Tarbell, J. McTiernan, G. Valori, T. Wiegelmann, M.S. Wheatland, T. Amari, G. Aulanier, P. Demoulin, M. Fuhrmann, K. Kusano, S. Regnier, and J.K. Thalmann
Projects: Hinode

Publication Status: ApJ (in press)
Last Modified: 2007-12-01 08:29
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Observations and Modelling of the 29 March 2014 X1 Flare   

Magnus Woods   Submitted: 2017-01-25 02:50

On the 29 March 2014 NOAA active region (AR) 12017 produced an X1 flare which was simultaneously observed by an unprecedented number of observatories. We have investigated the pre-flare period of this flare from 14:00 UT until 19:00 UT using joint observations made by the Interface Region Imaging Spectrometer (IRIS) and the Hinode Extreme Ultraviolet Imaging Spectrometer (EIS). Spectral lines providing coverage of the solar atmosphere from chromosphere to the corona were analysed to investigate pre-flare activity within the AR. The results of the investigation have revealed evidence of strongly blue-shifted plasma flows, with velocities up to 200 km/s, being observed 40 minutes prior to flaring. These flows are located along the filament present in the active region and are both spatially ... [READ MORE]

Authors: M. M. Woods, L. K. Harra, S. A. Matthews, D. H. Mackay, S. Dacie, D. M. Long
Projects: Hinode/EIS,IRIS

Publication Status: Accepted for publication in Solar Physics
Last Modified: 2017-01-25 10:27
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Magnetic and Kinetic Power Spectra as a Tool to Probe the Turbulent Dynamo   

Valentyna Abramenko   Submitted: 2011-12-16 10:27

Generation and diffusion of the magnetic field on the Sun is a key mechanism responsible for solar activity on all spatial and temporal scales - from the solar cycle down to the evolution of small-scale magnetic elements in the quiet Sun. The solar dynamo operates as a non-linear dynamical process and is thought to be manifest in two types: as a global dynamo responsible for the solar cycle periodicity, and as a small-scale turbulent dynamo responsible for the formation of magnetic carpet in the quiet Sun. Numerous MHD simulations of the solar turbulence did not yet reach a consensus as to the existence of a turbulent dynamo on the Sun. At the same time, high-resolution observations of the quiet Sun from Hinode instruments suggest possibilities for the turbulent dynamo. Analysis of ... [READ MORE]

Authors: Valentyna Abramenko, Vasyl Yurchyshyn, Philip Googe
Projects: Hinode/SOT

Publication Status: accepted in ASP Conference Series
Last Modified: 2011-12-19 09:07
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Coronal nonthermal velocity following helicity injection before an X-class flare   

Louise Harra   Submitted: 2009-01-13 01:17

We explore the ''pre-flare'' behavior of the corona in the three-day period building up to the X-class flare on 2006 Dec 13, by analyzing the EUV spectral profiles from the Hinode EUV Imaging Spectrometer (EIS) instrument. We found an increase in the coronal spectral line widths, beginning after the time of saturation of the injected helicity as measured by citet{magara}. In addition, this increase in line widths (indicating non-thermal motions) starts before any eruptive activity occurs. Hinode EIS has the sensitivity to measure changes in the build up to a flare many hours before the flare begins.

Authors: Harra, Williams, Wallace, Magara, Hara, Tsuneta, Sterling and Doschek
Projects: Hinode/EIS

Publication Status: published
Last Modified: 2009-01-14 08:47
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Triggering Process of the X1.0 Three-ribbon Flare in the Great Active Region NOAA 12192   

Yumi Bamba   Submitted: 2017-04-03 20:04

The solar magnetic field in a flare-producing active region (AR) is much more complicated than theoretical models, which assume a very simple magnetic field structure. The X1.0 flare, which occurred in AR 12192 on 2014 October 25, showed a complicated three-ribbon structure. To clarify the trigger process of the flare and to evaluate the applicability of a simple theoretical model, we analyzed the data from Hinode/Solar Optical Telescope and the Solar Dynamics Observatory/Helioseismic and Magnetic Imager, Atmospheric Imaging Assembly. We investigated the spatio-temporal correlation between the magnetic field structures, especially the non-potentiality of the horizontal field, and the bright structures in the solar atmosphere. As a result, we determined that the western side of the ... [READ MORE]

Authors: Y. Bamba, S. Inoue, K. Kusano, and D. Shiota
Projects: Hinode/SOT,SDO-AIA,SDO-HMI

Publication Status: Published
Last Modified: 2017-04-04 08:09
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Subject will be restored when possible   

Yin Zhang   Submitted: 2008-06-24 01:59

In this letter we report a close relationship between the variations of the transport rate of the magnetic helicity dH/dt and the microwave burst. The latter may be regarded as a prompt signal of non-thermal energetic particles originated from the magnetic reconnection during solar flaring events. We analyze the observations of magnetograms of MDI/SOHO and SOT/Hinode, and the high-cadence microwave observation at 2.84 GHz obtained in Chinese Solar Broadband Radiospectrometer (SRBS/Huairou) of a flare/CME event which occurred in Active Region NOAA 10930 on 2006 December 13. We find that there is a sharp jump of dH/dt around the onset and quench of the microwave burst at the frequency of 2.84 GHz: the rate of dH/dt changes from negative to positive around the start of the ... [READ MORE]

Authors: Y. Zhang., B. L. Tan, and Y. H. Yan
Projects: Hinode/SOT,SoHO-MDI

Publication Status: accepted
Last Modified: 2008-09-23 20:59
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Subject will be restored when possible   

Ramon Oliver   Submitted: 2008-03-19 02:48

Recent observations with the Hinode Solar Optical Telescope display an active region prominence whose fine threads oscillate in the vertical direction as they move along a path parallel to the photosphere. A seismological analysis of this event is carried out by taking advantage of the small radius of these structures compared to the total length of magnetic field lines, i.e. by using the thin tube approximation. This analysis reveals that the oscillatory period is only slightly modified by the existence of the flow and that the difference between the period of a flowing thread and a static one is below the error bars of these observations. Moreover, although it is not possible to obtain values of the physical parameters, a lower bound for the Alfv'en speed (ranging between 120 km ... [READ MORE]

Authors: J. Terradas, I. Arregui, R. Oliver, J. L. Ballester
Projects: Hinode/SOT

Publication Status: ApJ (in press)
Last Modified: 2008-09-23 21:13
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Plasma parameters and geometry of cool and warm active region loops   

Maria Madjarska   Submitted: 2017-05-09 16:57

How the solar corona is heated to high temperatures remains an unsolved mystery in solar physics. In the present study we analyse observations of 50 whole active-region loops taken with the Extreme-ultraviolet Imaging Spectrometer (EIS) on board the Hinode satellite. Eleven loops were classified as cool (<1 MK) and 39 as warm (1-2 MK) loops. We study their plasma parameters such as densities, temperatures, filling factors, non-thermal velocities and Doppler velocities. We combine spectroscopic analysis with linear force-free magnetic-field extrapolation to derive the three-dimensional structure and positioning of the loops, their lengths and heights as well as the magnetic field strength along the loops. We use density-sensitive line pairs from Fe XII, Fe XIII, Si X and Mg VII ions to ... [READ MORE]

Authors: Haixia Xie, Maria S. Madjarska, Bo Li, Zhenghua Huang, Lidong Xia, Thomas Wiegelmann, Hui Fu, Chaozhou Mou
Projects: Hinode/EIS

Publication Status: ApJ, accepted for publication
Last Modified: 2017-05-10 09:18
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Confirming a Seismologically Inferred Coronal Temperature   

Mike Marsh   Submitted: 2009-10-20 06:33

The Extreme-Ultraviolet Imaging Spectrometer on board the HINODE satellite is used to examine the loop system described in Marsh et al. (2009) by applying spectroscopic diagnostic methods. A simple isothermal mapping algorithm is applied to determine where the assumption of isothermal plasma may be valid, and the emission measure locii technique is used to determine the temperature profile along the base of the loop system. It is found that, along the base, the loop has a uniform temperature profile with a mean temperature of 0.89 +- 0.09 MK which is in agreement with the temperature determined seismologically in Marsh et al. (2009), using observations interpreted as the slow magnetoacoustic mode. The results further strengthen the slow mode interpretation, propagation at a uniform sound ... [READ MORE]

Authors: M.S. Marsh and R.W. Walsh
Projects: Hinode/EIS

Publication Status: ApJL, 2009, 706, 76
Last Modified: 2009-11-02 07:54
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Three-dimensional MHD modeling of propagating disturbances in fan-like coronal loops   

Tongjiang Wang   Submitted: 2013-08-13 10:30

Quasi-periodic propagating intensity disturbances (PDs) have been observed in large coronal loops in EUV images over a decade, and are widely accepted to be slow magnetosonic waves. However, spectroscopic observations from Hinode/EIS revealed their association with persistent coronal upflows, making this interpretation debatable. Motivated by the scenario that the coronal upflows could be cumulative result of numerous individual flow pulses generated by sporadic heating events (nanoflares) at the loop base, we construct a velocity driver with repetitive tiny pulses, whose energy frequency distribution follows the flare power-law scaling. We then perform 3D MHD modeling of an idealized bipolar active region by applying this broadband velocity driver at the footpoints of large coronal loops ... [READ MORE]

Authors: Tongjiang Wang, Leon Ofman, and Joseph M. Davila
Projects: Hinode/EIS,SDO-AIA

Publication Status: Accepted by ApJ Letters in August 2013
Last Modified: 2013-08-13 11:02
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Using the transit of Venus to probe the upper planetary atmosphere   

Fabio Reale   Submitted: 2015-07-01 04:11

During a planetary transit, atoms with high atomic number absorb short-wavelength radiation in the upper atmosphere, and the planet should appear larger during a primary transit observed in high-energy bands than in the optical band. Here we measure the radius of Venus with subpixel accuracy during the transit in 2012 observed in the optical, ultraviolet and soft X-rays with Hinode and Solar Dynamics Observatory missions. We find that, while Venus?s optical radius is about 80 km larger than the solid body radius (the top of clouds and haze), the radius increases further by >70 km in the extreme ultraviolet and soft X-rays. This measures the altitude of the densest ion layers of Venus?s ionosphere (CO2 and CO), useful for planning missions in situ, and a benchmark case for detecting ... [READ MORE]

Authors: Fabio Reale, Angelo F. Gambino, Giuseppina Micela, Antonio Maggio, Thomas Widemann, Giuseppe Piccioni
Projects: Hinode/XRT,SDO-AIA

Publication Status: published in Nature Communications
Last Modified: 2015-07-01 20:30
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Active Region Moss: Basic Physical Parameters and Their Temporal Variation   

Durgesh Tripathi   Submitted: 2010-05-18 03:04

Context. Active region moss are transition region phenomena, first noted in the images recorded by the Transition Region and Coronal Explorer (TRACE) in λ171. Moss regions are thought to be the footpoints of hot loops (3-5 MK) seen in the core of active regions. These hot loops appear ?fuzzy? (unresolved). Therefore, it is difficult to study the physical plasma parameters in individual hot core loops and hence their heating mechanisms. Moss regions provide an excellent opportunity to study the physics of hot loops. In addition, they allow us to study the transition region dynamics in the footpoint regions. Aims. To derive the physical plasma parameters such as temperature, electron density, and filling factors in moss regions and to study their variation over a short ... [READ MORE]

Authors: D. Tripathi, H. E. Mason, G. Del Zanna, P. R. Young
Projects: Hinode/EIS

Publication Status: Accepted for publication in Astronomy and Astrophysics
Last Modified: 2010-05-18 11:52
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What Dominates the Coronal Emission Spectrum During the Cycle of Impulsive Heating and Cooling?   

Stephen Bradshaw   Submitted: 2011-09-06 09:18

The 'smoking gun' of small-scale, impulsive events heating the solar corona is expected to be the presence of hot (>5 MK) plasma. Evidence for this has been scarce, but has gradually begun to accumulate due to recent studies designed to constrain the high-temperature part of the emission measure distribution. However, the detected hot component is often weaker than models predict and this is due in part to the common modeling assumption that the ionization balance remains in equilibrium. The launch of the latest generation of space-based observing instrumentation on board Hinode and the Solar Dynamics Observatory (SDO) has brought the matter of the ionization state of the plasma firmly to the forefront. It is timely to consider exactly what emission current instruments would detect ... [READ MORE]

Authors: Bradshaw, S.J., Klimchuk, J.A.
Projects: Hinode/EIS,SDO-AIA

Publication Status: Published
Last Modified: 2011-09-06 11:15
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The Role of Transient Brightenings in Heating the Solar Corona   

David Brooks   Submitted: 2008-12-02 21:58

Nanoflare reconnection events have been proposed as a mechanism for heating the corona. Parker's original suggestion was that frequent reconnection events occur in coronal loops due to the braiding of the magnetic field. Many observational studies, however, have focused on the properties of isolated transient brightenings unassociated with loops, but their cause, role, and relevance for coronal heating have not yet been established. Using Hinode SOT magnetograms and high-cadence EIS spectral data we study the relationship between chromospheric, transition region, and coronal emission and the evolution of the magnetic field. We find that hot, relatively steadily emitting coronal loops and isolated transient brightenings are both associated with magnetic flux regions that are highly ... [READ MORE]

Authors: David H. Brooks, Ignacio Ugarte-Urra, Harry P. Warren
Projects: Hinode/EIS,Hinode/SOT

Publication Status: Published in ApJL, 689, L77
Last Modified: 2008-12-03 13:24
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Subject will be restored when possible   

Hiroko Watanabe   Submitted: 2007-11-21 00:59

High resolution imaging observation of a sunspot umbra was done with Hinode Solar Optical Telescope (SOT). Filtergrams in wavelengths of blue and green continuum were taken during three consecutive days. The umbra consisted of a dark core region, several diffuse components and numerous umbral dots. We derived basic properties of umbral dots (UDs), especially their temperatures, lifetimes, proper motions, spatial distribution and morphological evolution. Brightness of UDs is confirmed to depend on the bright- ness of their surrounding background. Several UDs show fission and fusion. Thanks to the stable condition of space observation, we could first follow the temporal behavior of these events. The derived properties of internal structure of the umbra are discussed in viewpoint of ... [READ MORE]

Authors: Reizaburo Kitai, Hiroko Watanabe, Tahei Nakamura, Ken-ichi Otsuji, Takuma Matsumoto, Satoru UeNo, Shin-ichi Nagata, Kazunari Shibata, Richard Muller, Kiyoshi Ichimoto, Saku Tsuneta, Yoshinori Suematsu, Yukio Katsukawa, Toshifumi Shimizu, Theodore D. Tarbell, Richard A. Shine, Alan M. Title, Bruce W. Lites
Projects: Hinode

Publication Status: Published in PASJ 59 (Hinode Special Issue), astro-ph/0711.3266
Last Modified: 2008-01-07 03:14
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An Updated View of Solar Eruptive Flares and Development of Shocks and CMEs: History of the 2006 December 13 GLE-Productive Extreme Event   

Victor Grechnev   Submitted: 2013-08-13 21:20

An extreme 2006 December 13 event marked the onset of the Hinode era being the last major flare in the solar cycle 23 observed with NoRH and NoRP. The event produced a fast CME, strong shock, and big particle event responsible for GLE70. We endeavor to clarify relations between eruptions, shock wave, and the flare, and to shed light on a debate over the origin of energetic protons. One concept relates it with flare processes. Another one associates acceleration of ions with a bow shock driven by a CME at (2-4)R_sun. The latter scenario is favored by a delayed particle release time after the flare. However, our previous studies have established that a shock wave is typically excited by an impulsively erupting magnetic rope (future CME core) during the flare rise, while the outer CME ... [READ MORE]

Authors: V. Grechnev, V. Kiselev, A. Uralov, N. Meshalkina, A. Kochanov
Projects: GOES X-rays ,Hinode/SOT,Hinode/XRT,Nobeyama Radioheliograph,RHESSI,SoHO-EIT,SoHO-MDI,SoHO-LASCO,SXI

Publication Status: Accepted for publication in PASJ
Last Modified: 2013-08-14 08:28
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Magnetohydrodynamic Simulations for Studying Solar Flare Trigger Mechanism   

Johan Muhamad   Submitted: 2017-06-22 19:51

In order to understand the flare trigger mechanism, we conduct three-dimensional magnetohydrodynamic simulations using a coronal magnetic field model derived from data observed by the Hinode satellite. Several types of magnetic bipoles are imposed into the photospheric boundary of the Non-linear Force-Free Field (NLFFF) model of Active Region NOAA 10930 on 2006 December 13 to investigate what kind of magnetic disturbance may trigger the flare. As a result, we confirm that certain small bipole fields, which emerge into the highly sheared global magnetic field of an active region, can effectively trigger a flare. These bipole fields can be classified into two groups based on their orientation relative to the polarity inversion line: the so called opposite polarity (OP) and reversed shear ... [READ MORE]

Authors: Johan Muhamad, Kanya Kusano, Satoshi Inoue, Daikou Shiota
Projects: Hinode/SOT,Hinode/XRT

Publication Status: Published in ApJ
Last Modified: 2017-06-28 08:41
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A self-consistent nonlinear force-free solution for a solar active region magnetic field   

Mike Wheatland   Submitted: 2009-06-24 01:13

Nonlinear force-free solutions for the magnetic field in the solar corona constructed using photospheric vector magnetic field boundary data suffer from a basic problem: the observed boundary data are inconsistent with the nonlinear force-free model. Specifically, there are two possible choices of boundary conditions on vertical current provided by the data, and the two choices lead to different force-free solutions. A novel solution to this problem is described. Bayesian probability is used to modify the boundary values on current density, using field-line connectivity information from the two force-free solutions and taking into account uncertainties, so that the boundary data are more consistent with the two nonlinear force-free solutions. This procedure may be iterated ... [READ MORE]

Authors: M.S. Wheatland and S. Regnier
Projects: Hinode/SOT

Publication Status: Accepted for publication in ApJ Letters
Last Modified: 2009-06-24 07:27
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On the Effectiveness of Multi-Instrument Solar Flare Observations During Solar Cycle 24   

Ryan Milligan   Submitted: 2017-03-14 04:08

Our current fleet of space-based solar observatories offer us a wealth of opportunities to study solar flares over a range of wavelengths, and the greatest advances in our understanding of flare physics often come from coordinated observations between different instruments. However, despite considerable effort to coordinate this armada of instruments over the years (e.g. through the Max Millennium Program of Solar Flare Research), there are few solar flares that have been observed by most or all available instruments simultaneously, due to the combination of each instrument's operational constraints. Here we describe a technique that retrospectively searches archival databases for flares jointly observed by RHESSI, SDO/EVE (MEGS-A and MEGS-B), Hinode/(EIS, SOT and XRT), and IRIS. Out of ... [READ MORE]

Authors: Ryan Milligan, Jack Ireland
Projects: GOES/EUVS,GOES X-rays,Hinode/EIS,Hinode/SOT,Hinode/XRT,IRIS,PROBA2/SWAP,RHESSI,SDO-EVE

Publication Status: Submitted to Solar Physics
Last Modified: 2017-03-14 11:48
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The Diagnostics of the Kappa-Distributions from EUV Spectra   

Elena Dzifcakova   Submitted: 2010-03-03 03:19

The EUV lines suitable to diagnose possible kappa-distributions in the solar corona are examined. A set of synthetic spectra for various values of the kappa-parameter, characterising the non-thermal kappa-distributions, electron densities, and the mean energy of the distributions are calculated in the spectral range corresponding to the Hinode EIS and Coronas-F/SPIRIT detectors. The strong EUV lines of Fe in various degrees of ionization are used to analyse the sensitivity of the line ratios to the shape of the distribution function, electron density, and temperature or the parameter T of the kappa-distribution. The EUV lines suitable for the diagnostics of the distribution function are proposed and the conditions for their usage are discussed.

Authors: Dzifcakova, E. and Kulinova, A.
Projects: Hinode/EIS

Publication Status: Solar. Phys. (accepted}
Last Modified: 2010-03-03 07:49
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Local Helioseismology of Sunspots: Current Status and Perspectives (Invited Review)   

Alexander Kosovichev   Submitted: 2011-02-23 14:19

Mechanisms of the formation and stability of sunspots are among the longest-standing and intriguing puzzles of solar physics and astrophysics. Sunspots are controlled by subsurface dynamics hidden from direct observations. Recently, substantial progress in our understanding of the physics of the turbulent magnetized plasma in strong-field regions has been made by using numerical simulations and local helioseismology. Both the simulations and helioseismic measurements are extremely challenging, but it becomes clear that the key to understanding the enigma of sunspots is a synergy between models and observations. Recent observations and radiative MHD numerical models have provided a convincing explanation to the Evershed flows in sunspot penumbrae. Also, they lead to the understanding of ... [READ MORE]

Authors: A.G. Kosovichev
Projects: GONG,Hinode/SOT,SoHO-MDI

Publication Status: submitted to Solar Physics
Last Modified: 2011-02-24 08:40
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Correlation Between Sharp Variation of the Transport Rate of Magnetic Helicity and Solar Eruptive Events   

Yin Zhang   Submitted: 2008-06-24 01:59

In this letter we report a close relationship between the variations of the transport rate of the magnetic helicity dH/dt and the microwave burst. The latter may be regarded as a prompt signal of non-thermal energetic particles originated from the magnetic reconnection during solar flaring events. We analyze the observations of magnetograms of MDI/SOHO and SOT/Hinode, and the high-cadence microwave observation at 2.84 GHz obtained in Chinese Solar Broadband Radiospectrometer (SRBS/Huairou) of a flare/CME event which occurred in Active Region NOAA 10930 on 2006 December 13. We find that there is a sharp jump of dH/dt around the onset and quench of the microwave burst at the frequency of 2.84 GHz: the rate of dH/dt changes from negative to positive around the start of the ... [READ MORE]

Authors: Y. Zhang., B. L. Tan, and Y. H. Yan
Projects: Hinode/SOT,SoHO-MDI

Publication Status: ApJL, in press
Last Modified: 2008-09-23 20:59
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Lagrangian coherent structures in photospheric flows and their implications for coronal magnetic structure   

Anthony Yeates   Submitted: 2012-06-21 07:01

Aims. We show how the build-up of magnetic gradients in the Sun's corona may be inferred directly from photospheric velocity data. This enables computation of magnetic connectivity measures such as the squashing factor without recourse to magnetic field extrapolation. Methods.Assuming an ideal evolution in the corona, and an initially uniform magnetic field, the subsequent field line mapping is computed by integrating trajectories of the (time-dependent) horizontal photospheric velocity field. The method is applied to a 12 hour high-resolution sequence of photospheric flows derived from Hinode/SOT magnetograms. Results. We find the generation of a network of quasi-separatrix layers in the magnetic field, which correspond to Lagrangian coherent structures in the photospheric velocity. ... [READ MORE]

Authors: A.R. Yeates, G. Hornig, and B.T. Welsch
Projects: Hinode/SOT

Publication Status: A&A 539, A1, 2012
Last Modified: 2012-06-21 09:17
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Subject will be restored when possible   

Leon Ofman   Submitted: 2008-03-27 05:36

Aims. We report the first evidence for transverse waves in coronal multithreaded loops with cool plasma ejected from the chromosphere flowing along the threads. These observations are good candidates for coronal seismology. Methods. We analyzed observations made with Solar Optical Telescope (SOT) on board the Hinode satellite in the Ca II H line filter. Results. The oscillations are visible for about 3 periods, with a period lasting about 2 minutes, with weak damping. We see the oscillations in thin threads (~0.5'') of cool plasma flowing in the coronal loops with speeds in the range 74-123 km/s. Conclusions. Observations indicate that the waves exhibit different properties in the various threads. In some threads, the waves are nearly standing fundamental kink modes with a phase ... [READ MORE]

Authors: L. Ofman and T.J. Wang
Projects: Hinode/SOT

Publication Status: in press
Last Modified: 2008-09-23 21:12
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Three-dimensional Structure of a Solar Active Region from Spatially and Spectrally Resolved Microwave Observations   

Samuel Tun   Submitted: 2010-11-10 21:20

We report on the structure of the solar atmosphere above active region AR 10923, observed on 2006 Nov 10, as deduced from multi-wavelength studies including combined microwave observations from the Very Large Array (VLA) and the Owens Valley Solar Array (OVSA). The VLA observations provide excellent image quality at a few widely spaced frequencies while the OVSA data provide information at many intermediate frequencies to fill in the spectral coverage. Images at 25 distinct frequencies are used to provide spatially resolved spectra along many lines of sight in the active region, from which microwave spectral diagnostics are obtained for deducing maps of temperature, magnetic field, and column density. The derived quantities are compared with multiwavelength observations from SoHO and ... [READ MORE]

Authors: S. D. Tun, D. E. Gary, M. K. Georgoulis
Projects: Hinode/SOT,Hinode/XRT,SoHO-EIT,SoHO-MDI,Very Large Array,Owens Valley Solar Array

Publication Status: ApJ (accepted)
Last Modified: 2010-11-11 10:59
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Spectroscopic Signatures Related to a Sunquake   

Sarah Matthews   Submitted: 2015-08-31 05:26

The presence of flare related acoustic emission (sunquakes) in some flares, and only in specific locations within the flaring environment, represents a severe challenge to our current understanding of flare energy transport processes. In an attempt to contribute to understanding the origins of sunquakes we present a comparison of new spectral observations from Hinode's EUV imaging Spectrometer (EIS) and the Interface Region Imaging Spectrograph (IRIS) of the chromosphere, transition region and corona above a sunquake, and compare them to the spectra observed in a part of the flaring region with no acoustic signature. Evidence for the sunquake is determined using both time-distance and acoustic holography methods, and we find that, unlike many previous sunquake detections, the signal is ... [READ MORE]

Authors: Sarah A. Matthews, Louise K. harra, Sergei Zharkov & Lucie M. Green
Projects: GOES X-rays ,Hinode/EIS,IRIS,RHESSI,SDO-AIA,SDO-HMI

Publication Status: ApJ (accepted)
Last Modified: 2015-08-31 09:41
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On the Area Expansion of Magnetic Flux-Tubes in Solar Active Regions   

Jaroslav Dudik   Submitted: 2014-09-25 07:45

We calculated the 3D distribution of the area expansion factors in a potential magnetic field extrapolated from the high-resolution \textit{Hinode}/SOT magnetogram of a quiescent active region NOAA 11482. Retaining only closed loops within the computational box, we show that the distribution of area expansion factors show significant structure. Loop-like structures characterized by locally lower values of the expansion factor are embedded in a smooth background. These loop-like flux-tubes have squashed cross-sections and expand with height. The distribution of the expansion factors show overall increase with height, allowing an active region core characterized by low values of the expansion factor to be distinguished. The area expansion factors obtained from extrapolation of the SOT ... [READ MORE]

Authors: Dudik, J., Dzifcakova, E., Cirtain, J. W.
Projects: Hinode/SOT

Publication Status: The Astrophysical Journal, accepted
Last Modified: 2014-09-25 15:58
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Magnetic Field Structures Triggering Solar Flares and Coronal Mass Ejections   

Kanya Kusano   Submitted: 2012-10-02 22:14

Solar flares and coronal mass ejections (CMEs), the most catastrophic eruptions in our solar system, have been known to affect terrestrial environments and infrastructure. However, because their triggering mechanism is still not sufficiently understood, our capacity to predict the occurrence of solar eruptions and to forecast space weather is substantially hindered. Even though various models have been proposed to determine the onset of solar eruptions, the types of magnetic structures capable of triggering these eruptions are still unclear. In this study, we solved this problem by systematically surveying the nonlinear dynamics caused by a wide variety of magnetic structures in terms of three-dimensional magnetohydrodynamic simulations. As a result, we determined that two different types ... [READ MORE]

Authors: K. Kusano, Y. Bamba, T. T. Yamamoto, Y. Iida, S. Toriumi, A. Asai
Projects: Hinode/SOT

Publication Status: ApJ, in press
Last Modified: 2012-10-03 11:25
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Benchmarking atomic data for astrophysics: Fe VIII EUV lines   

Giulio Del Zanna   Submitted: 2009-11-20 15:38

The EUV spectrum of Fe VIII is reviewed, using new solar observations from the Hinode EUV Imaging Spectrometer (EIS), together with older solar and laboratory data. The most up-to-date scattering calculations are benchmarked against these experimental data, with the use of a large atomic structure calculation. Once adjustments are made to the excitation rates, good agreement is found between calculated and observed line intensities. All previous line identifications have been re-assessed. Several lines are identified here for the first time, most notably the strong decays from the 3s2 3p5 3d2 4D_j levels. It is shown that they provide a new, important diagnostic of electron temperature for the upper transition region. The temperatures obtained at the base of solar coronal ... [READ MORE]

Authors: Del Zanna, G.
Projects: Hinode/EIS

Publication Status: A&A in press
Last Modified: 2009-11-23 13:51
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Does a polar coronal hole?s flux emergence follow a Hale-like law?   

Edward DeLuca   Submitted: 2009-07-30 09:15

Recent increases in spatial and temporal resolution for solar telescopes sensitive to EUV and X-ray radiation have revealed the prevalence of transient jet events in polar coronal holes. Using data collected by the X-Ray Telescope on Hinode, Savcheva et al. (2007) confirmed the observation, made first by the Soft X-ray Telescope on Yohkoh, that some jets exhibit a motion transverse to the jet outflow direction. The velocity of this transverse motion is, on average, 20 km s−1 . The direction of the transverse motion, in combination with the standard reconnection model for jet production (e.g. Shibata et al. 1992), reflects the magnetic polarity orientation of the ephemeral active region at the base of the jet. From this signature, we find that during the ... [READ MORE]

Authors: A. Savcheva , J.W. Cirtain , E.E. DeLuca , L. Golub
Projects: Hinode/XRT

Publication Status: ApJ in press
Last Modified: 2009-07-30 11:14
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Subject will be restored when possible   

Cristina Chifor   Submitted: 2008-01-14 06:32

Aims: We study the physical properties of an active region (AR) jet in order to probe the mechanisms responsible for it. Methods: We report 2007 January 15/16 observations of a recurring jet situated on the west side of NOAA AR 10938. Multi-wavelength data from all three instruments onboard Hinode were analysed. This paper focuses on one instance of a jet observed with the Hinode/EUV Imaging Spectrometer (EIS). Using EIS raster data we measured the temperatures, Doppler shifts, density, and filling factor. Results: A strong blue-shifted component and an indication of a weak red-shifted component at the base of the jet was observed around Log T_e= 6.2. The up-flow velocities exceeded 150 km/s. The jet component was seen over a range of temperatures between 5.4 and 6.4 in Log T_e. Using ... [READ MORE]

Authors: C. Chifor, P. R. Young, H. Isobe, H. E. Mason, D. Tripathi, H. Hara, T. Yokoyama
Projects: Hinode/EIS,Hinode/SOT,Hinode/XRT

Publication Status: A&A Letters (Hinode special edition) , in press
Last Modified: 2008-01-14 07:21
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Subject will be restored when possible   

Louise Harra   Submitted: 2008-03-26 02:00

The formation of the slow solar wind has been debated for many years. In this paper we show evidence of persistent outflow at the edges of an active region as measured by the EUV Imaging Spectrometer onboard Hinode. The Doppler velocity ranged between 20-50 km/s and was consistent with a steady flow seen in the X-ray Telescope. The latter showed steady, pulsing outflowing material and some transverse motions of the loops. We analyse the magnetic field around the active region and produce a coronal magnetic field model. We determine from the latter that the outflow speeds adjusted for line-of-sight effects can reach over 100 km/s. We can interpret this outflow as expansion of loops that lie over the active region, which may either reconnect with neighbouring large-scale loops or are ... [READ MORE]

Authors: Harra, Sakao, Mandrini,Hara, Imada, Young, van Driel-Gesztelyi, Baker
Projects: Hinode/EIS

Publication Status: ApJ Letters, 676, L147, 2008
Last Modified: 2008-09-23 21:12
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Youra Taroyan   Submitted: 2008-01-31 03:24

Standing slow (acoustic) waves commonly observed in hot coronal loops offer a unique opportunity to understand the properties of the coronal plasma. The lack of evidence for similar oscillations in cooler loops is still a puzzle. The high cadence EIS instrument on board recently launched Hinode has the capability to detect wave motion in EUV lines both in the imaging and spectroscopy modes. The paper aims to establish the distinct characteristics of standing and propagating acoustic waves and to predict their footprints in EIS data. A 1D hydrodynamic loop model is used and the consequences of various types of heating pulses are examined. In each case, the resulting hydrodynamic evolution of the loop is converted into observables using a selection of available EIS spectral lines and ... [READ MORE]

Authors: Y. Taroyan, S. Bradshaw
Projects: Hinode/EIS

Publication Status: Astron. Astrophys. 2008, in press
Last Modified: 2008-01-31 09:11
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Hiroko Watanabe   Submitted: 2008-04-06 23:38

A high resolution imaging observation of a sunspot umbra was made with the Hinode Solar Optical Telescope. Filtergrams at wavelengths of the blue and green continua were taken during three consecutive days. The umbra consisted of a dark core region, several diffuse components, and numerous umbral dots. We derived basic properties of umbral dots (UDs), especially their temperatures, lifetimes, proper motions, spatial distribution, and morphological evolution. The brightness of UDs is confirmed to depend on the brightness of their surrounding background. Several UDs show fission and fusion. Thanks to the stable condition of the space observation, we could for the first time follow the temporal behavior of these events. The derived properties of the internal ... [READ MORE]

Authors: Reizaburo Kitai, Hiroko Watanabe, Tahei Nakamura, Ken-ichi Otsuji, Takuma Matsumoto, Satoru UeNo, Shin-ichi Nagata, Kazunari Shibata, Richard Muller, Kiyoshi Ichimoto, Saku Tsuneta, Yoshinori Suematsu, Yukio Katsukawa, Toshifumi Shimizu, Theodore D. Tarbell, Richard A. Shine, Alan M. Title, Bruce W. Lites
Projects: Hinode/SOT

Publication Status: Published in PASJ 59 (Hinode Special Issue), astro-ph/0711.3266
Last Modified: 2008-09-23 21:11
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Dr. A. K. Srivastava   Submitted: 2008-03-14 01:39

Aims. To study intensity oscillations in the solar chromosphere/corona above a quiet-Sun magnetic network. Methods. We analyse the time series of He II 256.32, Fe XI 188.23 and Fe XII 195.12 spectral lines observed by EUV Imaging Spectrometer (EIS) on board Hinode near the south pole. Then we use a standard wavelet tool to produce power spectra of intensity oscillations above the magnetic network. Results. We get ~7 min intensity oscillations in all spectral lines and ~13 min intensity oscillations only in He II with the probability of ~96-98 %, which probably reflects the process of magneto-acoustic wave propagation above the network. Conclusions. We suggest that field-free cavity areas under bipolar magnetic canopies in the vicinity of magnetic network may serve as resonators for the ... [READ MORE]

Authors: A.K. Srivastava, D. Kuridze, T.V. Zaqarashvili, & B.N. Dwivedi
Projects: Hinode/EIS

Publication Status: Accepted in A&A Letters (unedited version from arXive.)
Last Modified: 2008-09-23 21:14
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3D magnetic field configuration of small-scale reconnection events in the solar plasma atmosphere   

Toshifumi Shimizu   Submitted: 2015-08-24 18:43

The outer solar atmosphere, i.e., the corona and the chromosphere, is replete with small energy-release events, which are accompanied by transient brightening and jet-like ejections. These events are considered to be magnetic reconnection events in the solar plasma, and their dynamics have been studied using recent advanced observations from the Hinode spacecraft and other observatories in space and on the ground. These events occur at different locations in the solar atmosphere, and vary in their morphology and amount of the released energy. The magnetic field configurations of these reconnection events are inferred based on observations of magnetic fields at the photospheric level. Observations suggest that these magnetic configurations can be classified into two groups. In the first ... [READ MORE]

Authors: T. Shimizu
Projects: Hinode/SOT

Publication Status: Accepted for publications in Physics of Plasmas
Last Modified: 2015-08-25 16:48
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The 3D geometry of active region upflows deduced from their limb-to-limb evolution   

Pascal Demoulin   Submitted: 2012-11-28 02:51

We analyse the evolution of coronal plasma upflows from the edges of AR 10978, which has the best limb-to-limb data coverage with Hinode's EUV Imaging Spectrometer (EIS). We find that the observed evolution is largely due to the solar rotation progressively changing the viewpoint of nearly stationary flows. From the systematic changes in the upflow regions as a function of distance from disc centre, we deduce their 3D geometrical properties as inclination and angular spread in three coronal lines (SiVII, FeXII, FeXV). In agreement with magnetic extrapolations, we find that the flows are thin, fan-like structures rooted in quasi separatrix layers (QSLs). The fans are tilted away from the AR centre. The highest plasma velocities in these three spectral lines have similar magnitudes and ... [READ MORE]

Authors: Demoulin, P., Baker, D., Mandrini, C.H., Van Driel-Gesztelyi, L.
Projects: Hinode/EIS

Publication Status: Solar Physics (in press)
Last Modified: 2012-11-28 09:41
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Temperature and Electron Density Diagnostics of a Candle-flame-shaped Flare   

Silvina Guidoni   Submitted: 2015-02-10 08:20

Candle-flame-shaped flares are archetypical structures that provide indirect evidence of magnetic reconnection. A flare resembling Tsuneta's famous 1992 candle-flame flare occurred on 2011 January 28; we present its temperature and electron density diagnostics. This flare was observed with Solar Dynamics Observatory/Atmospheric Imaging Assembly (SDO/AIA), Hinode/X-Ray Telescope (XRT), and Solar Terrestrial Relations Observatory Ahead (STEREO-A)/Extreme Ultraviolet Imager, resulting in high-resolution, broad temperature coverage, and stereoscopic views of this iconic structure. The high-temperature images reveal a brightening that grows in size to form a tower-like structure at the top of the posteruption flare arcade, a feature that has been observed in other long-duration events. Despite ... [READ MORE]

Authors: S. E. Guidoni, D. E. McKenzie, D. W. Longcope, J. E. Plowman, and K. Yoshimura
Projects: Hinode/XRT,SDO-AIA,STEREO

Publication Status: ApJ, published
Last Modified: 2015-02-11 12:23
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Flare Energy Build-Up in a Decaying Active Region Near a Coronal Hole   

Yingna Su   Submitted: 2009-08-25 10:01

A B1.7 two-ribbon flare occurred in a highly non-potential decaying active region near a coronal hole at 10:00 UT on May 17, 2008. This flare is ?large? in the sense that it involves the entire region, and it is associated with both a filament eruption and a CME. We present multi-wavelength observations from EUV (TRACE, STEREO/EUVI), X-rays (Hinode/XRT), and Hα (THEMIS, BBSO) prior to, during and after the flare. Prior to the flare, the region contained two filaments. The long J-shaped sheared loops corresponding to the southern filament were evolved from two short loop systems, which happened around 22:00 UT after a filament eruption on May 16. Formation of highly sheared loops in the south eastern part of the region was observed ... [READ MORE]

Authors: Yingna Su, Adriaan van Ballegooijen, Brigitte Schmieder, Arkadiusz Berlicki, Yang Guo, Leon Golub, Guangli Huang
Projects: Hinode/XRT

Publication Status: 2009, ApJ, v. 704, p. 341-353
Last Modified: 2011-04-06 09:05
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Yihua Yan   Submitted: 2007-10-08 04:16

On 2006 December 13 during the solar minimum, the superactive region NOAA 10930 at S05W33 disk location produced an X3.4/4B flare at 02:40 UT. Fine structures were observed in the radio spectra, which include spikes, reverse slope type III bursts, type U burst, V-shaped burst, pulsations, zebra patterns and firstly-discovered sub-second spiky zebra-like structures, superimposed in the 2.6 -- 3.8 GHz type IV bursts. The radio fine structures during the impulsive phase of the flare may be closely associated with coronal structures during the magnetic reconnection process as revealed by {Hinode} soft X-ray images. Thus these microwave fine structure observations may provide very useful diagnostics in the primary energy release sites when they occur in the impulsive flare phase. For this ... [READ MORE]

Authors: Yihua Yan, Jing Huang, Bin Chen, Takashi Sakurai
Projects: Hinode,RHESSI,SoHO-MDI

Publication Status: PASJ Vol.59, 2007 (Hinode special issue, in press)
Last Modified: 2007-10-08 17:18
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Observation and Simulation of Longitudinal Oscillations of an Active Region Prominence   

Qingmin Zhang   Submitted: 2012-04-17 08:35

{Filament longitudinal oscillations have been observed on the solar disk in H$alpha$.} {We intend to find an example of the longitudinal oscillations of a prominence, where the magnetic dip can be seen directly, and examine what is the restoring force of such kind of oscillations.} {We carry out a multiwavelength data analysis of the active region prominence oscillations above the western limb on 2007 February 8. Besides, we perform a one-dimensional hydrodynamic simulation of the longitudinal oscillations.} {The high-resolution observations by Hinode/SOT indicate that the prominence, seen as a concave-inward shape in lower-resolution Extreme Ultraviolet (EUV) images, actually consists of many concave-outward threads, which is ... [READ MORE]

Authors: Qingmin Zhang, Pengfei Chen, Chun Xia, Rony Keppens
Projects: Hinode/SOT

Publication Status: accepted
Last Modified: 2012-04-17 13:55
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Subject will be restored when possible   

Yihua Yan   Submitted: 2007-10-08 04:16

On 2006 December 13 during the solar minimum, the superactive region NOAA 10930 at S05W33 disk location produced an X3.4/4B flare at 02:40 UT. Fine structures were observed in the radio spectra, which include spikes, reverse slope type III bursts, type U burst, V-shaped burst, pulsations, zebra patterns and firstly-discovered sub-second spiky zebra-like structures, superimposed in the 2.6 -- 3.8 GHz type IV bursts. The radio fine structures during the impulsive phase of the flare may be closely associated with coronal structures during the magnetic reconnection process as revealed by {Hinode} soft X-ray images. Thus these microwave fine structure observations may provide very useful diagnostics in the primary energy release sites when they occur in the impulsive flare phase. For this ... [READ MORE]

Authors: Yihua Yan, Jing Huang, Bin Chen, Takashi Sakurai
Projects: Hinode,RHESSI,SoHO-MDI

Publication Status: PASJ Vol.59, 2007 (Hinode special issue, in press)
Last Modified: 2007-10-08 17:20
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Magnetic topology of Active Regions and Coronal Holes: Implications for Coronal Outflows and the Solar Wind   

Pascal Demoulin   Submitted: 2012-07-20 10:23

During 2 ? 18 January 2008 a pair of low-latitude opposite-polarity coronal holes (CHs) were observed on the Sun with two active regions (ARs) and the heliospheric plasma sheet located between them. We use the Hinode/EUV Imaging Spectrometer (EIS) to locate AR-related outflows and measure their velocities. Solar-Terrestrial Relations Observatory (STEREO) imaging is also employed as are the Advanced Composition Explorer (ACE) in-situ observations, to assess the resulting impacts on the interplanetary solar wind (SW) properties. Magnetic field extrapolations of the two ARs confirm that AR plasma outflows observed with EIS are co-spatial with quasi-separatrix layer locations, including the separatrix of a null point. Global potential field source-surface modeling indicates that field lines ... [READ MORE]

Authors: L. van Driel-Gesztelyi, J. L. Culhane, D. Baker, P. D?moulin, C.H. Mandrini, M.L. DeRosa, A. P. Rouillard, A. Opitz, G. Stenborg, A. Vourlidas, D. H. Brooks
Projects: Hinode/EIS

Publication Status: Solar Physics (in press)
Last Modified: 2012-07-20 11:37
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Subject will be restored when possible   

Peter Young   Submitted: 2007-08-31 04:20

Quiet Sun and active region spectra from the Hinode/EIS instrument are presented, and the strongest lines from different temperature regions discussed. A list of emission lines recommended to be included in EIS observation studies is presented based on analysis of blending and diagnostic potential using the CHIANTI atomic database. In addition we identify the most useful density diagnostics from the ions covered by EIS.

Authors: P.R. Young, G. Del Zanna, H.E. Mason, K.P. Dere, E. Landi, M. Landini, G.A. Doschek, C.M. Brown, J.L. Culhane, L.K. Harra, T. Watanabe, H. Hara
Projects: Hinode

Publication Status: Accepted for PASJ Hinode special issue
Last Modified: 2007-08-31 18:06
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Observing Episodic Coronal Heating Events Rooted in Chromospheric Activity   

Scott McIntosh   Submitted: 2009-10-13 12:57

We present results of a multi-wavelength study of episodic plasma injection into the corona of AR 10942. We exploit long-exposure images of the Hinode and Transition Region and Coronal Explorer (TRACE) spacecraft to study the properties of faint, episodic, ''blobs'' of plasma that are propelled upward along coronal loops that are rooted in the AR plage. We find that the source location and characteristic velocities of these episodic upflow events match those expected from recent spectroscopic observations of faint coronal upflows that are associated with upper chromospheric activity, in the form of highly dynamic spicules. The analysis presented ties together observations from coronal and chromospheric spectrographs and imagers, providing more evidence of the connection of discrete ... [READ MORE]

Authors: Scott W. McIntosh & Bart De Pontieu
Projects: Hinode/SOT

Publication Status: in press ApJL.
Last Modified: 2009-10-14 07:58
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David Brooks   Submitted: 2008-01-30 00:50

Theoretically, magnetic fields are expected to expand as they rise above the photosphere and into the corona, so the apparent uniform cross-sections of active region loops are difficult to understand. There has been some debate as to whether coronal loops really have constant cross-sections, or are actually unresolved and composed of expanding threads within the constant cross-section envelopes. Furthermore, loop expansion is critical to the success or failure of hydrostatic models in reproducing the intensities and morphology of observed emission. We analyze Hinode EIS observations of loops in active region 10953 and detect only moderate apex width expansion over a broad range of temperatures from log T_e/K = 5.6 to 6.25. The expansion is less than required by steady-state ... [READ MORE]

Authors: D. H. Brooks, H. P. Warren, I. Ugarte-Urra, K. Matsuzaki, and D. R. Williams
Projects: Hinode/EIS

Publication Status: Published in PASJ Hinode Special Issue
Last Modified: 2008-01-30 09:37
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Benchmarking atomic data for astrophysics: Fe XVII EUV lines   

Giulio Del Zanna   Submitted: 2009-11-20 16:04

In the light of accurate structure and scattering calculations for Fe XVII, we review the status of identifications in the EUV spectrum of this ion using various experimental data, from the X-rays to the UV. Most previous identifications are confirmed, although a critical revision leads to changes in many wavelength values, in particular for the 2p5 3s--2p5 3p and 2p5 3p--2p5 3d transitions,which we observed with the Hinode EUV Imaging Spectrometer (EIS). Several lines are identified here for the first time. We find good agreement between expected and measured line intensities, with a few notable exceptions. In particular, the strong line in the EIS spectra, observed at 254.88 A, has a consistently low observed intensity. We present two Hinode/EIS observations and discuss ... [READ MORE]

Authors: Del Zanna, G. & Ishikawa, Y.
Projects: Hinode/EIS

Publication Status: A&A in press
Last Modified: 2009-11-23 13:51
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Urmila Mitra-Kraev   Submitted: 2008-02-01 15:18

With the Solar Optical Telescope on Hinode, we investigate the basic properties of high-degree solar oscillations observed at two levels in the solar atmosphere, in the G-band (formed in the photosphere) and in the Ca II H line (chromospheric emission). We analyzed the data by calculating the individual power spectra as well as the cross-spectral properties, i.e., coherence and phase shift. The observational properties are compared with a simple theoretical model, which includes the effects of correlated noise. The results reveal significant frequency shifts between the Ca II H and G-band spectra, in particular above the acoustic cut-off frequency for pseudo-modes. The cross-spectrum phase shows peaks associated with the acoustic oscillation (p-mode) lines, and begins to increase with ... [READ MORE]

Authors: U. Mitra-Kraev, A.G. Kosovichev, T. Sekii
Projects: Hinode/SOT

Publication Status: A&A Letters (Hinode Special Issue), in press
Last Modified: 2008-02-03 09:23
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Solar Magnetized Tornadoes: Rotational Motion in a Tornado-like Prominence   

Yang Su   Submitted: 2013-12-20 06:56

Su et al. 2012 proposed a new explanation for filament formation and eruption, where filament barbs are rotating magnetic structures driven by underlying vortices on the surface. Such structures have been noticed as tornado-like prominences when they appear above the limb. They may play a key role as the source of plasma and twist in filaments. However, no observations have successfully distinguished rotational motion of the magnetic structures in tornado-like prominences from other motions such as oscillation and counter-streaming plasma flows. Here we report evidence of rotational motions in a tornado-like prominence. The spectroscopic observations in two coronal lines were obtained from a specifically designed Hinode/EIS observing program. The data revealed the existence of both cold ... [READ MORE]

Authors: Yang Su, Peter G"{o}m"{o}ry, Astrid Veronig, Manuela Temmer, Tongjiang Wang, Kamalam Vanninathan, Weiqun Gan, Youping Li
Projects: Hinode/EIS,Other,SDO-AIA

Publication Status: accepted by ApJL
Last Modified: 2014-03-17 17:34
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Nonlinear Force-free Modeling of Magnetic Fields in a Solar Filament   

Ju Jing   Submitted: 2010-07-23 09:45

We present a striking filament pattern in the nonlinear force-free (NLFF) chromospheric magnetic field of the active region NOAA 10956. The NLFF chromospheric field is extrapolated from the Hinode high-resolution photospheric vector magnetogram using the weighted optimization method. The modeled structure is characterized by a highly sheared field with strong horizontal magnetic components and has a virtually identical shape and location as the filament seen in Hα. The modeled field strength agrees with the recent He I 10830 ? observations by Kuckein et al.. The unequivocal resemblance between the NLFF extrapolation and the Hα observation not only demonstrates the ability of the NLFF field to reproduce chromospheric features, but also provides a valuable diagnostic tool for the ... [READ MORE]

Authors: Ju Jing, Yuan Yuan, Thomas Wiegelmann, Yan Xu, Rui Liu and Haimin Wang
Projects: Hinode/SOT

Publication Status: The Astrophysical Journal Letters, 719, 56
Last Modified: 2010-07-27 02:46
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High speed photospheric material flow observed at the polarity inversion line of a delta-type sunspot producing an X5.4 flare on 7 March 2012   

Toshifumi Shimizu   Submitted: 2014-06-08 18:30

Solar flares abruptly release the free energy stored as a non-potential magnetic field in the corona and may be accompanied by eruptions of the coronal plasma. Formation of a non-potential magnetic field and the mechanisms for triggering the onset of flares are still poorly understood. In particular, photospheric dynamics observed near those polarity inversion lines that are sites of major flare production have not been well observed with high spatial resolution spectro-polarimetry. This paper reports on a remarkable high-speed material flow observed along the polarity inversion line located between flare ribbons at the main energy release side of an X5.4 flare on 7 March 2012. Observations were carried out by the spectro-polarimeter of the Solar Optical Telescope onboard Hinode. The ... [READ MORE]

Authors: Shimizu, T., Lites, B.W., and Bamba, Y.
Projects: Hinode/SOT

Publication Status: Accepted to PASJ, Hinode special issue
Last Modified: 2014-06-09 06:57
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Field Topology Analysis of a Long-Lasting Coronal Sigmoid   

Antonia Savcheva   Submitted: 2012-03-05 12:42

We present the first field topology analysis based on Non-Linear Force-Free Field (NLFFF) models of a long-lasting coronal sigmoid observed in February 2007 with the X-ray telescope on Hinode. The NLFFF models are built with the flux rope insertion method and give the 3D coronal magnetic field as constrained by observed coronal loop structures and photospheric magnetograms. Based on these models, we have computed horizontal maps of the current and the squashing factor Q for 25 different heights in the corona for all 6 days of the evolution of the region. We use the squashing factor to quantify the degree of change of the field line linkage and to identify prominent Quasi-Separatrix Layers (QSLs). We discuss the major properties of these QSL maps and devise a way to pick out important QSLs ... [READ MORE]

Authors: A. Savcheva, A. van Ballegooijen, E. DeLuca
Projects: Hinode/XRT

Publication Status: published
Last Modified: 2012-03-05 14:19
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Measuring the Magnetic Field Strength of the Quiet Solar Corona Using ''EIT Waves''   

David Long   Submitted: 2013-05-23 02:00

Variations in the propagation of globally-propagating disturbances (commonly called ''EIT waves'') through the low solar corona offer a unique opportunity to probe the plasma parameters of the solar atmosphere. Here, high-cadence observations of two ''EIT wave'' events taken using the Atmospheric Imaging Assembly (AIA) instrument onboard the Solar Dynamics Observatory (SDO) are combined with spectroscopic measurements from the Extreme ultraviolet Imaging Spectrometer (EIS) onboard the Hinode spacecraft and used to examine the variability of the quiet coronal magnetic-field strength. The combination of pulse kinematics from SDO/AIA and plasma density from Hinode/EIS is used to show that the magnetic-field strength is in the range ~2-6 G in the quiet corona. The magnetic-field estimates are ... [READ MORE]

Authors: David M. Long, David R. Williams, St?phane R?gnier, Louise K. Harra
Projects: Hinode/EIS,Hinode/SOT,SDO-AIA,SDO-HMI

Publication Status: Solar Physics (in press)
Last Modified: 2013-05-23 16:17
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The Effects of Initial Pitch-Angle Distributions on Flare Observables   

Henry Winter   Submitted: 2011-02-03 08:53

In this work we model both the thermal and non-thermal components of solar flares. The model we use, HyLoop, combines a hydrodynamic equation solver with a non-thermal particle tracking code to simulate the thermal and non-thermal dynamics and emission of solar flares. In order to test the effects of pitch-angle distribution on flare dynamics and emission, a series of flares are simulated with non-thermal electron beams injected at the loop apex. The pitch-angle distribution of each beam is described by a single parameter and allowed to vary from flare to flare. We use the results of these simulations to generate synthetic hard and soft X-ray emissions (HXR, & SXR). The lightcurves of the flares in Hinode's X-ray Telescope (XRT) passbands show a distinct signal that is a ... [READ MORE]

Authors: Henry D. Winter III, Petrus Martens, and Katharine K. Reeves
Projects: Hinode/XRT,RHESSI

Publication Status: Submitted
Last Modified: 2011-02-06 18:43
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Rapid Transition of Uncombed Penumbrae to Faculae during Large Flares   

Haimin Wang   Submitted: 2012-03-13 09:20

In the past two decades, the complex nature of sunspots has been disclosed with high-resolution observations. One of the most important findings is the ''uncombed'' penumbral structure, where a more horizontal magnetic component carrying most of Evershed Flows is embedded in a more vertical magnetic background (Solanki & Montavon 1993). The penumbral bright grains are locations of hot upflows and dark fibrils are locations of horizontal flows that are guided by nearly horizontal magnetic field. On the other hand, it was found that flares may change the topology of sunspots in $delta$ configuration: the structure at the flaring polarity inversion line becomes darkened while sections of peripheral penumbrae may disappear quickly and permanently associated with flares (Liu et al. 2005). The ... [READ MORE]

Authors: Haimin Wang, Na Deng, Chang Liu
Projects: GONG,Hinode/SOT,SoHO-MDI

Publication Status: Published in ApJ 2012, 748, 76
Last Modified: 2012-03-13 13:19
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Detection of Supergranulation Alignment in Polar Regions of the Sun by Helioseismology   

Kaori Nagashima   Submitted: 2010-12-10 11:41

We report on a new phenomenon of `alignment' of supergranulation cells in the polar regions of the Sun. Recent high-resolution datasets obtained by the Solar Optical Telescope (SOT) onboard the Hinode satellite enabled us to investigate supergranular structures in high-latitude regions of the Sun up to 80 degrees latitude. We have carried out a local helioseismology time-distance analysis of the data, and detected acoustic travel-time variations due to the supergranular flows. The supergranulation cells in both the north and south polar regions show systematic alignment patterns in the north-south direction. The south-pole datasets obtained in a month-long Hinode campaign indicate that the supergranulation alignment property may be quite common in the polar regions. We also discuss the ... [READ MORE]

Authors: Kaori Nagashima, Junwei Zhao, Alexander G. Kosovichev, Takashi Sekii
Projects: Hinode/SOT

Publication Status: Accepted for publication in ApJ Letters
Last Modified: 2010-12-10 11:48
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Emission Measure Distribution and Heating of Two Active Region Cores   

Durgesh Tripathi   Submitted: 2011-07-28 04:37

Using data from the Extreme-ultraviolet Imaging Spectrometer aboard Hinode, we have studied the coronal plasma in the core of two active regions. Concentrating on the area between opposite polarity moss, we found emission measure distributions having an approximate power-law form EM$propto T^{2.4}$ from $log,T = 5.5$ up to a peak at $log,T = 6.55$. We show that the observations compare very favorably with a simple model of nanoflare-heated loop strands. They also appear to be consistent with more sophisticated nanoflare models. However, in the absence of additional constraints, steady heating is also a viable explanation.

Authors: Durgesh Tripathi, James A. Klimchuk, Helen E. Mason
Projects: Hinode/EIS

Publication Status: Accepted for publication in The Astrophysical Journal
Last Modified: 2011-07-29 07:56
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Coronal Rain as a Marker for Coronal Heating Mechanisms   

Patrick Antolin   Submitted: 2010-05-15 05:42

Reported observations in Hα, Ca II H, and K or other chromospheric lines of coronal rain trace back to the days of the Skylab mission. Corresponding to cool and dense plasma, coronal rain is often observed falling down along coronal loops in active regions. A physical explanation for this spectacular phenomenon has been put forward thanks to numerical simulations of loops with footpoint-concentrated heating, a heating scenario in which cool condensations naturally form in the corona. This effect has been termed ''catastrophic cooling'' and is the predominant explanation for coronal rain. In this work, we further investigate the link between this phenomenon and the heating mechanisms acting in the corona. We start by analyzing observations of coronal rain at the limb in the Ca II H ... [READ MORE]

Authors: P. Antolin, K. Shibata and G. Vissers
Projects: Hinode/SOT

Publication Status: Published in ApJ
Last Modified: 2010-05-17 09:16
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Subject will be restored when possible   

John Mariska   Submitted: 2007-09-28 06:58

The EUV Imaging Spectrometer (EIS) on the Hinode satellite is capable of measuring emission line center positions for Gaussian line profiles to a fraction of a spectral pixel, resulting in relative solar Doppler-shift measurements with an accuracy of a less than a km/s for strong lines. We show an example of the application of that capability to an active region sit-and-stare observation in which the EIS slit is placed at one location on the Sun and many exposures are taken while the spacecraft tracking keeps the same solar location within the slit. For the active region examined (NOAA 10930), we find that significant intensity and Doppler-shift fluctuations as a function of time are present at a number of locations. These fluctuations appear to be similar to those observed in ... [READ MORE]

Authors: John T. Mariska, Harry P. Warren, Ignacio Ugarte-Urra, David H. Brooks, David R. Williams, and Hirohisa Hara
Projects: Hinode

Publication Status: PASJ special Hionde issue in press
Last Modified: 2007-09-29 21:41
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Propagating Transverse Waves in Soft X-ray Coronal Jets   

Soheil Vasheghani Farahani   Submitted: 2009-04-01 08:28

Aims. The theoretical model for magnetohydrodynamic (MHD) modes guided by a field-aligned plasma cylinder with a steady flow is adapted to interpret transverse waves observed in solar coronal hot jets, discovered with Hinode/XRT in terms of fast magnetoacoustic kink modes. Methods. Dispersion relations for linear magnetoacoustic perturbations of a plasma jet of constant cross-section surrounded by static magnetised plasma are used to determine the phase and group speeds of guided transverse waves and their relationship with the physical parameters of the jet and the background plasma. The structure of the perturbations in the macroscopic parameters of the plasma inside and outside the jet, and the phase relations between them are also established. Results. We obtained a convenient ... [READ MORE]

Authors: S.Vasheghani Farahani, T. Van Doorsselaere, E. Verwichte, and V.M. Nakariakov
Projects: Hinode/XRT

Publication Status: Published in A&A
Last Modified: 2010-09-05 11:14
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Response of the solar atmosphere to magnetic field evolution in a coronal hole region   

Shuhong Yang   Submitted: 2009-04-16 20:22

Context. Coronal holes (CHs) are deemed to be the sources of the fast solar wind streams that lead to recurrent geomagnetic storms and have been intensively investigated, but not all the properties of them are known well. Aims. We mainly research the response of the solar atmosphere to the magnetic field evolution in a CH region, such as magnetic flux emergence and cancellation for both network (NT) and intranetwork (IN). Methods. We study an equatorial CH observed simultaneously by HINODE and STEREO on July 27, 2007. The HINODE/SP maps are adopted to derive the physical parameters of the photosphere and to research the magnetic field evolution and distribution. The G band and Ca ii H images with high tempo-spatial resolution from HINODE/BFI and the multi-wavelength data from ... [READ MORE]

Authors: S. H. Yang, J. Zhang, C. L. Jin, L. P. Li, and H. Y. Duan
Projects: Hinode/SOT,SoHO-EIT,SoHO-MDI,STEREO

Publication Status: Accepted by A&A
Last Modified: 2009-04-17 08:19
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Subject will be restored when possible   

Marek Siarkowski   Submitted: 2008-05-29 06:10

We discuss here various methodologies and an optimal strategy of the temperature and emission measure diagnostics based on Hinode X-Ray Telescope data. As an example of our results we present determination of the temperature distribution of the X-rays emitting plasma using filters ratio method and three various methods of the calculation of the differential emission measure (DEM). We have found that all these methods give results similar to the two filters ratio method. Additionally, all methods of the DEM calculation gave similar solutions. We can state that the majority of the pairs of the Hinode filters allows one to derive the temperature and emission measure in the isothermal plasma approximation using standard diagnostic based on two filters ratio method. In cases of strong flares ... [READ MORE]

Authors: Siarkowski M., Falewicz R., Kepa A., and Rudawy P.
Projects: Hinode/XRT

Publication Status: Ann. Geophys. (in press)
Last Modified: 2008-09-23 21:01
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Multi-instrument observations of a failed flare eruption associated with MHD waves in a loop bundle   

Giuseppe Nistico   Submitted: 2016-12-06 17:44

We present observations of a B7.9-class flare that occurred on the 24th January, 2015, using the Atmopsheric Imaging Assembly (AIA) of the Solar Dynamics Observatory (SDO), the EUV Imaging Spectrometer (EIS) and the X-Ray Telescope of Hinode. The flare triggers the eruption of a dense cool plasma blob as seen in AIA 171\AA,\, which is unable to completely break out and remains confined within a local bundle of active region loops. During this process, transverse oscillations of the threads are observed. The cool plasma is then observed to descend back to the chromosphere along each loop strand. At the same time, a larger diffuse co-spatial loop observed in the hot wavebands of SDO/AIA and Hinode/XRT is formed, exhibiting periodic intensity variations along its length. The formation and ... [READ MORE]

Authors: G. Nistico, V. Polito, V. M. Nakariakov, G. del Zanna
Projects: None,Hinode/EIS,Hinode/XRT,SDO-AIA

Publication Status: accepted for publication in A&A
Last Modified: 2016-12-07 12:17
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Formation Heights of Extreme Ultraviolet Lines in an Active Region Derived by Correlation of Doppler Velocity and Magnetic Field   

Yang Guo   Submitted: 2010-03-11 03:52

We study the correlation heights, which indicate the formation heights of Extreme Ultraviolet (EUV) lines in an active region using observations from the EUV Imaging Spectrometer (EIS) and Solar Optical Telescope (SOT) on board Hinode. The nonlinear force-free field (NLFFF) optimization method is adopted to extrapolate the 3D magnetic fields to higher layers. Three subregions with different characteristics are selected in the active region for this study. The results show that the formation heights in different subregions vary with their different magnetic fields or velocity patterns. After solving the line blending problem between the He 2 256.32 AA and Si 10 256.37 AA lines by the double Gaussian curve fitting, we find that the transition region lies higher in a strong magnetic area. In ... [READ MORE]

Authors: Guo, Y., Ding, M. D., Jin, M., Wiegelmann, T.
Projects: Hinode/EIS,Hinode/SOT

Publication Status: ApJ (2009), 696, 1526
Last Modified: 2010-03-12 09:44
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Subject will be restored when possible   

Ayumi Asai   Submitted: 2008-06-05 23:36

We present a detailed examination of strongly blueshifted emission lines observed with the EUV Imaging Spectrometer on board the Hinode satellite. We found two kinds of blueshifted phenomenon associated with the X3.4 flare that occurred on 2006 December 13. One was related to a plasmoid ejection seen in soft X-rays. It was very bright in all the lines used for the observations. The other was associated with the faint arc-shaped ejection seen in soft X-rays. The soft X-ray ejection is thought to be an MHD fast-mode shock wave. This is therefore the first spectroscopic observation of an MHD fast-mode shock wave associated with a flare.

Authors: Ayumi Asai, Hirohisa Hara, Tetsuya Watanabe, Shinsuke Imada, Taro Sakao, Noriyuki Narukage, J. L. Culhane, G. A. Doschek
Projects: Hinode/EIS

Publication Status: ApJ (accepted; 2008, 684, in press)
Last Modified: 2008-09-23 21:00
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Spectroscopic Observations of Hot Lines Constraining Coronal Heating in Solar Active Regions   

Spiros Patsourakos   Submitted: 2009-03-24 09:03

EUV observations of warm coronal loops suggest that they are bundles of unresolved strands that are heated impulsively to high temperatures by nanoflares. The plasma would then have the observed properties (e.g., excess density compared to static equilibrium) when it cools into the 1-2 MK range. If this interpretation is correct, then very hot emission should be present outside of proper flares. It is predicted to be vey faint, however. A critical element for proving or refuting this hypothesis is the existence of hot, very faint plasmas which should be at amounts predicted by impulsive heating. We report on the first comprehensive spectroscopic study of hot plasmas in active regions. Data from the EIS spectrometer on Hinode were used to construct emission ... [READ MORE]

Authors: S. Patsourakos, J. A. Klimchuk
Projects: Hinode/EIS

Publication Status: ApJ 2009, in press
Last Modified: 2009-03-24 09:31
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On the nature of spectral line broadening in solar coronal dimmings   

Laurent Dolla   Submitted: 2011-02-24 04:34

We analyze the profiles of iron emission lines observed in solar coronal dimmings associated with coronal mass ejections, using the EUV Imaging Spectrometer on board Hinode. We quantify line profile distortions with empirical coefficients (asymmetry and peakedness) that compare the fitted Gaussian to the data. We find that the apparent line broadenings reported in previous studies are likely to be caused by inhomogeneities of flow velocities along the line of sight, or at scales smaller than the resolution scale, or by velocity fluctuations during the exposure time. The increase in the amplitude of Alfvén waves cannot, alone, explain the observed features. A double-Gaussian fit of the line profiles shows that, both for dimmings and active region loops, one component is nearly at ... [READ MORE]

Authors: Dolla, L. R. and Zhukov, A. N.
Projects: Hinode/EIS,STEREO

Publication Status: ApJ 2011, 730, 113
Last Modified: 2011-03-11 11:42
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Acoustic Power Absorption and its Relation with Vector Magnetic Field of a Sunspot   

Sanjay Gosain   Submitted: 2010-08-11 21:05

The distribution of acoustic power over sunspots shows an enhanced absorption near the umbra--penumbra boundary. Earlier studies revealed that the region of enhanced absorption coincides with the region of strongest transverse potential field. The aim of this paper is to (i) utilize the high-resolution vector magnetograms derived using Hinode SOT/SP observations and study the relationship between the vector magnetic field and power absorption and (ii) study the variation of power absorption in sunspot penumbrae due to the presence of spine-like radial structures. It is found that (i) both potential and observed transverse fields peak at a similar radial distance from the center of the sunspot, and (ii) the magnitude of the transverse field, derived from Hinode observations, is much larger ... [READ MORE]

Authors: Sanjay Gosain, S. K. Mathew and P. Venkatakrishnan
Projects: Hinode/SOT

Publication Status: In Press Solar Physics, Topical Issue on Helio-and-Astroseismology
Last Modified: 2010-08-12 09:47
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Deeper by the Dozen: Understanding the Cross-Field Temperature Distributions of Coronal Loops   

Joan Schmelz   Submitted: 2013-01-25 09:18

Spectroscopic analysis of coronal loops has revealed a variety of cross-field temperature distributions. Some loops appear to be isothermal while others require multithermal plasma. The EUV Imaging Spectrometer on Hinode has the spatial resolution and temperature coverage required for differential emission measure (DEM) analysis of coronal loops. Our results also use data from the X-Ray Telescope on Hinode as a high-temperature constraint. Of our 12 loops, two were post-flare loops with broad temperature distributions, two were narrow but not quite isothermal, and the remaining eight were in the mid range. We consider our DEM methods to be a significant advance over previous work, and it is also reassuring to learn that our findings are consistent with results available in the literature. ... [READ MORE]

Authors: Schmelz, J.T., Pathak, S. Jenkins, B.S., Worley, B.T.
Projects: Hinode/EIS

Publication Status: 2013, ApJ, 764, 53
Last Modified: 2013-01-28 09:28
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Subject will be restored when possible   

David E. McKenzie   Submitted: 2008-01-16 14:57

<i>Aims.</i> Coronal sigmoids are important sources of eruptions into interplanetary space, and a handful of models have been proposed to explain their characteristic S shape. However, the coronal X-ray images available to date have generally not had sufficient resolution to distinguish between these models. The goal of the present investigation is to determine whether the new observations from Hinode can help us to make such a distinction.<p> <i>Methods.</i> We present the first observations of a persistent coronal sigmoid obtained with the Hinode X-Ray Telescope (XRT). The excellent angular resolution of XRT (1 arcsecond per pixel) and the sigmoid's location near disk center combined to provide an unprecedented view of the formation and eruption of this ... [READ MORE]

Authors: McKenzie, David E., & Canfield, Richard C.
Projects: Hinode/XRT,SoHO-MDI

Publication Status: A&A Letters (accepted, in press)
Last Modified: 2008-01-16 14:57
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Vector Magnetic Fields and Current Helicities in Coronal Holes and Quiet Regions   

Shuhong Yang   Submitted: 2010-11-01 21:50

In the solar photosphere, many properties of coronal holes (CHs) are not known, especially vector magnetic fields. Using observations from Hinode, we investigate vector magnetic fields, current densities and current helicities in two CHs and compare them with two normal quiet regions (QRs) for the first time. We find that, in the CHs and QRs, the areas where large current helicities are located are mainly co-spatial with strong vertical and horizontal field elements both in shape and location. In the CHs, horizontal magnetic fields, inclination angles, current densities and current helicities are larger than those in the QRs. The mean vertical current density and current helicity, averaged over all the observed areas including the CHs and QRs, are approximately 0.008 A m^(-2) and 0.005 ... [READ MORE]

Authors: Shuhong Yang, Jun Zhang, Ting Li, Mingde Ding
Projects: Hinode/SOT

Publication Status: ApJ (accepted)
Last Modified: 2010-11-02 09:28
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Evidence for Partial Taylor Relaxation from Changes in Magnetic Geometry and Energy during a Solar Flare   

Sophie A. Murray   Submitted: 2012-12-27 05:10

Solar flares are powered by energy stored in the coronal magnetic field, a portion of which is released when the field reconfigures into a lower energy state. Investigation of sunspot magnetic field topology during flare activity is useful to improve our understanding of flaring processes. Here we investigate the deviation of the non-linear field configuration from that of the linear and potential configurations, and study the free energy available leading up to and after a flare. The evolution of the magnetic field in NOAA region 10953 was examined using data from Hinode/SOT-SP, over a period of 12 hours leading up to and after a GOES B1.0 flare. Previous work on this region found pre- and post-flare changes in photospheric vector magnetic field parameters of flux elements outside the ... [READ MORE]

Authors: Sophie A. Murray, D. Shaun Bloomfield, Peter T. Gallagher
Projects: Hinode/SOT

Publication Status: Accepted for publication in Astronomy and Astrophysics
Last Modified: 2012-12-27 11:07
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On the estimate of magnetic non-potentiality of sunspots derived using SOT/SP observations: Effect of polarimetric noise   

Sanjay Gosain   Submitted: 2010-07-14 13:25

The accuracy of Milne-Eddington (ME) inversions, used to retrieve the magnetic field vector, depends upon the signal-to-noise ratio (SNR) of the spectropolarimetric observations. The SNR in real observations varies from pixel to pixel, therefore the accuracy of the field vector also varies over the map. The aim of this work is to study the effect of polarimetric noise on the inference of magnetic field vector and the magnetic non-potentiality of a real sunspot. To this end, we use Hinode SOT/SP vector magnetogram of a real sunspot NOAA 10933 as an input to generate synthetic Stokes profiles under ME model assumptions. We then add normally-distributed polarimetric noise of the level 0.5% of continuum intensity to these synthetic profiles and invert them again using ME code. This ... [READ MORE]

Authors: Sanjay Gosain, Sanjiv Kumar Tiwari and P. Venkatakrishnan
Projects: Hinode/SOT

Publication Status: Accepted for publication in ApJ
Last Modified: 2010-07-15 07:48
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The Radiated Energy Budget Of Chromospheric Plasma In A Major Solar Flare Deduced From Multi-Wavelength Observations   

Ryan Milligan   Submitted: 2014-06-23 02:34

This paper presents measurements of the energy radiated by the lower solar atmosphere, at optical, UV, and EUV wavelengths, during an X-class solar flare (SOL2011-02-15T01:56) in response to an injection of energy assumed to be in the form of nonthermal electrons. Hard X-ray observations from RHESSI were used to track the evolution of the parameters of the nonthermal electron distribution to reveal the total power contained in flare accelerated electrons. By integrating over the duration of the impulsive phase, the total energy contained in the nonthermal electrons was found to be >2x10^{31} erg. The response of the lower solar atmosphere was measured in the free-bound EUV continua of H I (Lyman), He I, and He II, plus the emission lines of He II at 304A and H I (Lya) at 1216A by ... [READ MORE]

Authors: Ryan O. Milligan, Graham S. Kerr, Brian R. Dennis, Hugh S. Hudson, Lyndsay Fletcher, Joel C. Allred, Phillip C. Chamberlin, Jack Ireland, Mihalis Mathioudakis, & Francis P. Kennan
Projects: Hinode/SOT,RHESSI,SDO-AIA,SDO-EVE

Publication Status: ApJ, Accepted
Last Modified: 2014-06-23 12:07
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Full-Sun observations for identifying the source of the slow solar wind   

David Brooks   Submitted: 2015-05-28 21:16

Fast (>700 km s−1) and slow (~400 km s−1) winds stream from the Sun, permeate the heliosphere and influence the near-Earth environment. While the fast wind is known to emanate primarily from polar coronal holes, the source of the slow wind remains unknown. Here we identify possible sites of origin using a slow solar wind source map of the entire Sun, which we construct from specially designed, full-disk observations from the Hinode satellite, and a magnetic field model. Our map provides a full-Sun observation that combines three key ingredients for identifying the sources: velocity, plasma composition and magnetic topology and shows them as solar wind composition plasma outflowing on open magnetic field lines. The area coverage of the identified sources ... [READ MORE]

Authors: David H. Brooks, Ignacio Ugarte-Urra, Harry P. Warren
Projects: Hinode/EIS

Publication Status: Nature Communications, 6, 5947
Last Modified: 2015-05-30 04:31
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Constraining hot plasma in a non-flaring solar active region with FOXSI hard X-ray observations   

Lindsay Glesener   Submitted: 2015-01-23 16:54

We present new constraints on the high-temperature emission measure of a non-flaring solar active region using observations from the recently flown Focusing Optics X-ray Solar Imager (FOXSI) sounding rocket payload. FOXSI has performed the first focused hard X-ray (HXR) observation of the Sun in its first successful flight on 2012 November 2. Focusing optics, combined with small strip detectors, enable high-sensitivity observations with respect to previous indirect imagers. This capability, along with the sensitivity of the HXR regime to high-temperature emission, offers the potential to better characterize high-temperature plasma in the corona as predicted by nanoflare heating models. We present a joint analysis of the differential emission measure (DEM) of active region 11602 using ... [READ MORE]

Authors: Ishikawa, Shin-nosuke; Glesener, Lindsay; Christe, Steven; Ishibashi, Kazunori; Brooks, David H.; Williams, David R.; Shimojo, Masumi; Sako, Nobuharu; Krucker, S
Projects: Hinode/EIS,Hinode/XRT,Other

Publication Status: Published in PASJ
Last Modified: 2015-01-26 10:04
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Achieving Self-Consistent Nonlinear Force-free Modeling of Solar Active Regions   

Mike Wheatland   Submitted: 2010-12-16 16:07

A nonlinear force-free solution is constructed for the coronal magnetic field in NOAA solar active region AR 10953 based on a photospheric vector magnetogram derived from Hinode satellite observations on 30 April 2007, taking into account uncertainties in the boundary data and using improved methods for merging multiple-instrument data. The solution demonstrates the ''self-consistency'' procedure of Wheatland & Regnier (2009), for the first time including uncertainties. The self-consistency procedure addresses the problem that photospheric vector magnetogram data are inconsistent with the force-free model, and in particular that the boundary conditions on vertical electric current density are over-specified and permit the construction of two different nonlinear force-free solutions. The ... [READ MORE]

Authors: M.S. Wheatland & K.D. Leka
Projects: Hinode/SOT,SoHO-MDI

Publication Status: To appear in the Astrophysical Journal (accepted 15 Dec 2010)
Last Modified: 2010-12-17 09:40
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Quiescent Reconnection Rate Between Emerging Active Regions and Preexisting Field, with Associated Heating: NOAA AR 11112,   

Lucas Tarr   Submitted: 2013-12-12 08:47

When magnetic flux emerges from beneath the photosphere it displaces the preexisting field in the corona, and a current sheet generally forms at the boundary between the old and new magnetic domains. Reconnection in the current sheet relaxes this highly stressed configuration to a lower energy state. This scenario is most familiar, and most often studied, in flares, where the flux transfer is rapid. We present here a study of steady, quiescent flux transfer occurring at a rate three orders of magnitude below that in a large flare. In particular we quantify the reconnection rate, and related energy release, occurring as new polarity emerges to form NOAA Active Region 11112 ( extsf{SOL16 October 2010T00:00:00L205C117}) within a region of preexisting flux. A bright, low lying kernel of ... [READ MORE]

Authors: Tarr, L.A., Longcope, D.W., McKenzie, D.E., and Yoshimura, K.
Projects: Hinode/XRT,SDO-AIA,SDO-HMI

Publication Status: Accepted for publication in Solar Physics
Last Modified: 2013-12-12 11:37
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Photon Spectroscopy with Imaging X-Ray Instruments   

Kevin Reardon   Submitted: 2007-03-09 03:06

Individual X-ray photons in the keV energy range produce hundreds of photoelectrons in a single pixel of a CCD array detector. The number of photoelectrons produced is a linear function of the photon energy, allowing the measurement of spectral information with an imaging detector system. Most solar X-ray telescopes, such as Yohkoh/SXT and Hinode/XRT, use CCD detectors in an integrating mode and are designed to make temperature estimates from multiband filter photometry. We show how such instruments can be used in a new way to perform a limited type of this photon spectroscopy. By measuring the variance in intensity of a series of repeated images through a single filter of an X-ray source, the mean energy per detected photon can be determined. This energy is related to the underlying ... [READ MORE]

Authors: Labonte, B.J., Reardon,K.P.
Projects: Hinode,Yohkoh-SXT

Publication Status: Solar Physics, in press
Last Modified: 2007-03-09 09:50
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Subject will be restored when possible   

Ryan Milligan   Submitted: 2008-05-05 09:22

RHESSI and Hinode observations of a GOES B-class flare are combined to investigate the origin of 15 MK plasma. The absence of any detectable hard X-ray emission coupled with weak blueshifted emission lines (indicating upward velocities averaging only 14 km/s) suggests that this was a result of direct heating in the corona, as opposed to nonthermal electron precipitation causing chromospheric evaporation. These findings are in agreement with a recent hydrodynamical simulation of microflare plasmas which found that higher temperatures can be attained when less energy is used to accelerate electrons out of the thermal distribution. In addition, unusual redshifts in the 2 MK Fe XV line (indicating downward velocities of ∼14 km/s) were observed cospatial with one of the flare ribbons ... [READ MORE]

Authors: Ryan O. Milligan
Projects: Hinode/EIS,Hinode/SOT,Hinode/XRT,RHESSI

Publication Status: ApJL, accepted
Last Modified: 2008-09-23 21:02
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Vector magnetic fields and Doppler velocity structures around a cancellation site in the Quiet-Sun   

Yusuke Iida   Submitted: 2010-02-23 02:34

A cancellation is thought to be a basic process of the photospheric magnetic field and plays an important role in magnetic flux budget and in various solar activities. There are two major theoretical scenarios for this phenomena, i.e. the U-loop emergence and the Omega-loop submergence models. It is important to clarify which is the dominant process during the cancellation for the estimation of the solar magnetic flux transport through the surface. We study the vector magnetic field and velocity structures around a quiet Sun cancellation by using the Solar Optical Telescope on board Hinode satellite. Transverse magnetic field connecting the canceling magnetic features and strong long-lasting Doppler red-shift signal are found. The transverse field is observed in the first ... [READ MORE]

Authors: Y. Iida, T. Yokoyama, and K. Ichimoto
Projects: Hinode/SOT

Publication Status: accepted
Last Modified: 2010-02-24 08:08
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Subject will be restored when possible   

Yin Zhang   Submitted: 2008-06-24 01:59

In this letter we report a close relationship between the variations of the transport rate of the magnetic helicity dH/dt and the microwave burst. The latter may be regarded as a prompt signal of non-thermal energetic particles originated from the magnetic reconnection during solar flaring events. We analyze the observations of magnetograms of MDI/SOHO and SOT/Hinode, and the high-cadence microwave observation at 2.84 GHz obtained in Chinese Solar Broadband Radiospectrometer (SRBS/Huairou) of a flare/CME event which occurred in Active Region NOAA 10930 on 2006 December 13. We find that there is a sharp jump of dH/dt around the onset and quench of the microwave burst at the frequency of 2.84 GHz: the rate of dH/dt changes from negative to positive around the start of the ... [READ MORE]

Authors: Y. Zhang., B. L. Tan, and Y. H. Yan
Projects: Hinode/SOT

Publication Status: accepted
Last Modified: 2008-07-09 17:34
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Helical motion of magnetic flux tubes in the solar atmosphere   

Teimuraz Zaqarashvili   Submitted: 2008-07-04 02:29

Photospheric granulation may excite transverse kink pulses in anchored vertical magnetic flux tubes. The pulses propagate upwards along the tubes with the kink speed, while oscillating wakes are formed behind the wave front in a stratified atmosphere. The wakes oscillate at the kink cut-off frequency of stratified medium and gradually decay in time. When two or more consecutive kink pulses with different polarizations propagate in the same thin tube, then the wakes corresponding to different pulses may superimpose. The superposition sets up helical motions of magnetic flux tubes in the photosphere/chromosphere as seen by recent Hinode movies. The energy carried by the pulses is enough to heat the solar chrmosphere/corona and accelerate the solar wind.

Authors: Zaqarashvili, T.V. and Skhirtladze, N.
Projects: Hinode/SOT

Publication Status: ApJL (accepted)
Last Modified: 2008-09-23 20:57
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Flows at the Edge of an Active Region: Observation and Interpretation   

Eric Buchlin   Submitted: 2012-04-09 14:21

Upflows observed at the edges of active regions have been proposed as the source of the slow solar wind. In the particular case of Active Region (AR) 10942, where such an upflow has been already observed, we want to evaluate the part of this upflow that actually remains confined in the magnetic loops that connect AR10942 to AR10943. Both active regions were visible simultaneously on the solar disk and were observed by STEREO/SECCHI EUVI. Using Hinode/EIS spectra, we determine the Doppler shifts and densities in AR10943 and AR10942, in order to evaluate the mass flows. We also perform magnetic field extrapolations to assess the connectivity between AR10942 and AR10943. AR10943 displays a persistent downflow in Fe XII. Magnetic extrapolations including both ARs show that this downflow can ... [READ MORE]

Authors: C. Boutry, E. Buchlin, J.-C. Vial, S. R?gnier
Projects: Hinode/EIS

Publication Status: Accepted for publication in ApJ
Last Modified: 2012-04-10 11:29
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The Influence of Spatial Resolution on Nonlinear Force-Free Modeling   

Marc DeRosa   Submitted: 2015-08-25 12:25

The nonlinear force-free field (NLFFF) model is often used to describe the solar coronal magnetic field, however a series of earlier studies revealed difficulties in the numerical solution of the model in application to photospheric boundary data. We investigate the sensitivity of the modeling to the spatial resolution of the boundary data, by applying multiple codes that numerically solve the NLFFF model to a sequence of vector magnetogram data at different resolutions, prepared from a single Hinode/SOT-SP scan of NOAA Active Region 10978 on 2007 December 13. We analyze the resulting energies and relative magnetic helicities, employ a Helmholtz decomposition to characterize divergence errors, and quantify changes made by the codes to the vector magnetogram boundary data in order to be ... [READ MORE]

Authors: M. L. DeRosa, M. S. Wheatland, K. D. Leka, G. Barnes, T. Amari, A. Canou, S. A. Gilchrist, J. K. Thalmann, G. Valori, T. Wiegelmann, C. J. Schrijver, A. Malanushenko, X. Sun, S. R?gnier
Projects: Hinode/SOT

Publication Status: ApJ (in press)
Last Modified: 2015-08-25 16:45
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Plasma composition of a sigmoidal anemone active region   

Deb Baker   Submitted: 2013-10-03 08:54

Using spectra obtained by the EIS instrument onboard Hinode, we present a detailed spatially resolved abundance map of an active region (AR) - coronal hole (CH) complex that covers an area of 359 arcsec x  485 arcsec. The abundance map provides fi rst ionization potential (FIP) bias levels in various coronal structures within the large EIS fi eld of view. Overall, FIP bias in the small, relatively young AR is 2-3. This modest FIP bias is a consequence of the AR age, its weak heating, and its partial reconnection with the surrounding CH. Plasma with a coronal composition is concentrated at AR loop footpoints, close to where fractionation is believed to take place in the chromosphere. In the AR, we found a moderate positive correlation of FIP bias with nonthermal velocity and magnetic ... [READ MORE]

Authors: D. Baker, D. H. Brooks, P. Demoulin, L. Gesztelyi, L. M. Green, J. Carlyle
Projects: Hinode/EIS

Publication Status: Accepted ApJ
Last Modified: 2013-10-05 20:20
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Subject will be restored when possible   

Yingna Su   Submitted: 2008-09-22 13:44

We present multi-wavelength observations of a simple bipolar active region (NOAA 10953), which produced several small flares (mostly B class and one C8.5 class) and filament activations from April 30 to May 3 in 2007. We also explore non-linear force free field (NLFFF) modeling of this region prior to the C8.5 flare on May 2, using magnetograph data from SOHO/MDI and Hinode/SOT. A series of NLFFF models are constructed using the flux-rope insertion method. By comparing the modeled field lines with multiple X-ray loops observed by Hinode/XRT, we find that the axial flux of the flux rope in the best-fit models is 7e20 Mx, while the poloidal flux has a wider range of (0.1--10)e10 Mx/cm. The axial flux in the best-fit model is well below the upper limit (~15e20 Mx) for stable force-free ... [READ MORE]

Authors: Yingna Su, Adriaan van Ballegooijen, Bruce W. Lites, Edward E. Deluca, Leon Golub, Paolo C. Grigis, Guangli Huang, and Haisheng Ji
Projects: Hinode/XRT

Publication Status: Accepted by ApJ, 2008
Last Modified: 2008-09-22 13:44
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Vector Magnetic Fields of Solar Granulation   

Chunlan Jin   Submitted: 2008-09-16 21:19

Observations of the quiet Sun from the Solar Optical Telescope/Spectro-Polarimeter (SOT/SP) aboard the Hinode spacecraft reveal the magnetic characteristics of the solar photosphere. By making use of the deep mode observations of three quiet regions, we have statistically s tudied the vector magnetic fields of solar granulation. More than 2000 normal granules are manually selected to form a sample. It is recognized that some granules are even darker than the mean photosphere in intensity, and there is a linear correlation between intensity and Doppler velocity in granules.

The distributions of longitudinal and transverse apparent magnetic flux densities, Doppler velocity and continuum intensity of granules are obtained, and their unsigned magnetic flux measured. Two ... [READ MORE]

Authors: Chunlan Jin, Jingxiu Wang, and Meng Zhao
Projects: Hinode/SOT

Publication Status: ApJ Submitted
Last Modified: 2008-09-16 21:23
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Subject will be restored when possible   

Sam Krucker   Submitted: 2007-10-31 16:44

This letter presents X-ray observations of a partially limb-occulted solar flare taken by the Reuven Ramaty High Energy Solar Spectroscopic Imager (RHESSI) and the X-ray telescope (XRT) onboard Hinode. Thermal emission originates from a simple loop at the western limb that rises slowly (~7 km/s) until the flare peak time. Above 18 keV, faint non-thermal emission with a hard/flat spectrum (gamma ~ 4) and fast time variations (of the order of tens of seconds) is seen that comes from a loop slightly above (~2000 km) the thermal loop, if compared at the same time. However, the non-thermal loop agrees well in altitude with the thermal flare loop seen later, at the soft X-ray peak time. This is consistent with simple flare models where non-thermal electrons in a flare loop ... [READ MORE]

Authors: Sam Krucker, I.G. Hannah, R.P. Lin
Projects: Hinode,RHESSI

Publication Status: accepted
Last Modified: 2007-11-01 07:23
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Automated Coronal Hole Detection Using Local Intensity Thresholding Techniques   

Larisza D. Krista   Submitted: 2009-05-12 04:08

We identify coronal holes using a histogram-based intensity thresholding technique and compare their properties to fast solar wind streams at three different points in the heliosphere. The thresholding technique was tested on EUV and X-ray images obtained using instruments onboard STEREO, SOHO and Hinode. The full-disk images were transformed into Lambert equal-area projection maps and partitioned into a series of overlapping sub-images from which local histograms were extracted. The histograms were used to determine the threshold for the low intensity regions, which were then classified as coronal holes or filaments using magnetograms from the SOHO/MDI. For all three instruments, the local thresholding algorithm was found to successfully determine coronal hole boundaries in a consistent ... [READ MORE]

Authors: Larisza D. Krista, Peter T. Gallagher
Projects: Hinode/XRT,SoHO-EIT,SoHO-MDI,STEREO

Publication Status: published
Last Modified: 2009-05-12 07:28
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Subject will be restored when possible   

David Brooks   Submitted: 2008-01-30 00:49

Theoretically, magnetic fields are expected to expand as they rise above the photosphere and into the corona, so the apparent uniform cross-sections of active region loops are difficult to understand. There has been some debate as to whether coronal loops really have constant cross-sections, or are actually unresolved and composed of expanding threads within the constant cross-section envelopes. Furthermore, loop expansion is critical to the success or failure of hydrostatic models in reproducing the intensities and morphology of observed emission. We analyze Hinode EIS observations of loops in active region 10953 and detect only moderate apex width expansion over a broad range of temperatures from $log$ $T_e$/K = 5.6 to 6.25. The expansion is less than required by ... [READ MORE]

Authors: D. H. Brooks, H. P. Warren, I. Ugarte-Urra, K. Matsuzaki, and D. R. Williams
Projects: Hinode/EIS

Publication Status: Published in PASJ Hinode Special Issue
Last Modified: 2008-01-30 00:49
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The coronal energy input from magnetic braiding   

Anthony Yeates   Submitted: 2014-04-16 01:57

We estimate the energy input into the solar corona from photospheric footpoint motions, using observations of a plage region by the Hinode Solar Optical Telescope. Assuming a perfectly ideal coronal evolution, two alternative lower bounds for the Poynting flux are computed based on field line footpoint trajectories, without requiring horizontal magnetic field data. When applied to the observed velocities, a bound based solely on displacements between the two footpoints of each field line is tighter than a bound based on relative twist between field lines. Depending on the assumed length of coronal magnetic field lines, the higher bound is found to be reasonably tight compared with a Poynting flux estimate using an available vector magnetogram. It is also close to the energy input ... [READ MORE]

Authors: Yeates, A.R., Bianchi, F., Welsch, B. T., Bushby, P. J.
Projects: Hinode/SOT

Publication Status: Accepted for publication in A&A
Last Modified: 2014-04-16 13:13
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Subject will be restored when possible   

Hiroko Watanabe   Submitted: 2007-11-21 00:59

High resolution imaging observation of a sunspot umbra was done with Hinode Solar Optical Telescope (SOT). Filtergrams in wavelengths of blue and green continuum were taken during three consecutive days. The umbra consisted of a dark core region, several diffuse components and numerous umbral dots. We derived basic properties of umbral dots (UDs), especially their temperatures, lifetimes, proper motions, spatial distribution and morphological evolution. Brightness of UDs is confirmed to depend on the bright- ness of their surrounding background. Several UDs show fission and fusion. Thanks to the stable condition of space observation, we could first follow the temporal behavior of these events. The derived properties of internal structure of the umbra are discussed in viewpoint of ... [READ MORE]

Authors: Reizaburo Kitai, Hiroko Watanabe, Tahei Nakamura, Ken-ichi Otsuji, Takuma Matsumoto, Satoru UeNo, Shin-ichi Nagata, Kazunari Shibata, Richard Muller, Kiyoshi Ichimoto, Saku Tsuneta, Yoshinori Suematsu, Yukio Katsukawa, Toshifumi Shimizu, Theodore D. Tarbell, Richard A. Shine, Alan M. Title, Bruce W. Lites
Projects: Hinode

Publication Status: ccepted for publication in PASJ (Hinode Special Issue), astro-ph/0711.3266
Last Modified: 2007-11-21 11:20
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Evidence from EIS for axial filament rotation before a large flare   

David Williams   Submitted: 2009-02-04 00:02

In this article, we present observations made with the Extreme-ultraviolet Imaging Spectrometer (EIS) on-board the Hinode solar satellite, of an active region filament in the He II emission line at 256.32 ?. The host active region (AR 10930) produces an X-class flare during these observations. We measure Doppler shifts with apparent velocities of up to 20 km/s, which are antisymmetric about the filament length and occur several minutes before the flare?s impulsive phase. This is indicative of a rotation of the filament, which is in turn consistent with expansion of a twisted flux rope due to the MHD helical kink instability. This is the first time that such an observation has been possible in this transition-region line, and we note ... [READ MORE]

Authors: Williams, D. R., Harra, L. K., Brooks, D. H., Imada, S., Hansteen, V. H.
Projects: Hinode/EIS

Publication Status: Accepted for publication in PASJ (Vol. 61, No. 3, June 2009)
Last Modified: 2009-02-04 08:44
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Flows and Motions in Moss in the Core of a Flaring Active Region: Evidence for Steady Heating   

David Brooks   Submitted: 2011-04-12 00:27

We present new measurements of the time variability of intensity, Doppler, and nonthermal velocities in moss in an active region core observed by the EUV Imaging Spectrometer on Hinode in 2007 June. The measurements are derived from spectral profiles of the Fe XII 195 Å line. Using the 2'' slit, we repeatedly scanned 150'' by 150'' in a few minutes. This is the first time it has been possible to make such velocity measurements in the moss, and the data presented are the highest cadence spatially resolved maps of moss Doppler and nonthermal velocities ever obtained in the corona. The observed region produced numerous C- and M-class flares with several occurring in the core close to the moss. The magnetic field was therefore clearly changing in the ... [READ MORE]


Authors: David H. Brooks, Harry P. Warren
Projects: Hinode/EIS

Publication Status: Published in ApJL, 703, L10
Last Modified: 2011-04-12 08:45
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AIA Observations of Hot Flare Plasma   

Kathy Reeves   Submitted: 2011-01-04 09:05

We present observations of hot plasma from solar eruptions recorded by the Atmospheric Imaging Assembly (AIA) on the Solar Dynamics Observatory (SDO). AIA is the first narrowband instrument capable of taking images of hot plasma in the 5-15 MK range. We find that there are hot structures above flare loops, and that they are typically more diffuse and nebulous than the well-defined flare loops. Because of the narrowband response, high sensitivity and high spatial resolution of AIA, these supra-arcade structures are visible in exquisite detail, particularly in the 131~AA and 94~AA channels. In one event, a C4.9 flare observed on 3 November 2010, hot plasma is seen to outline an erupting plasmoid, and possibly a current sheet. We compare hot plasma observed with AIA to structures ... [READ MORE]

Authors: Reeves, K. K and Golub, L.
Projects: Hinode/XRT

Publication Status: accepted in ApJL
Last Modified: 2011-01-04 13:19
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Sideways displacement of penumbral fibrils by the solar flare on 2006 December 13   

Leping Li   Submitted: 2010-06-30 20:05

Flares are known to restructure the magnetic field in the corona and to accelerate the gas between the field lines, but their effect on the photosphere is less well studied. New data of the Solar Optical Telescope (SOT) onboard Hinode provide unprecedented opportunity to uncover the photospheric effect of a solar flare, which associates with an active region NOAA AR 10930 on 2006 December 13. We find a clear lateral displacement of sunspot penumbral regions scanned by two flare ribbons. In the impulsive phase of the flare, the flare ribbons scan the sunspot at a speed of around 18 km/s, derived from Ca II and G-band images. We find instantaneous horizontal shear of penumbral fibrils, with initial velocities of about 1.6 km/s, produced when a flare ribbon passes over them. This velocity ... [READ MORE]

Authors: Jun Zhang, Leping Li, S. K. Solanki
Projects: Hinode/SOT

Publication Status: Accepted by ApJL
Last Modified: 2010-07-02 14:55
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Physical Properties of White-Light Sources in the 2011 Feb 15 Solar Flare   

Graham Stewart Kerr   Submitted: 2014-01-20 19:07

White light flares (WLFs) are observational rarities, making them understudied events. However, optical emission is a significant contribution to flare energy budgets and the emission mechanisms responsible could have important implications for flare models. Using Hinode SOT optical continuum data taken in broadband red, green and blue filters, we investigate white-light emission from the X2.2 flare SOL2011-02-15T01:56:00. We develop a technique to robustly identify enhanced flare pixels and, using a knowledge of the RGB filter transmissions, determined the source color temperature and effective temperature. We investigated two idealized models of WL emission - an optically thick photospheric source, and an optically thin chromospheric slab. Under the optically thick assumption, the color ... [READ MORE]

Authors: Kerr, G.S & Fletcher, L.
Projects: Hinode/SOT

Publication Status: ApJ (in press)
Last Modified: 2014-01-20 19:10
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Magneto-seismological insights into the penumbral chromosphere and evidence for wave damping in spicules   

Richard Morton   Submitted: 2014-05-14 01:50

The observation of propagating magneto-hydrodynamic kink waves in magnetic structures and measurement of their properties (amplitude, phase speed) can be used to diagnose the plasma conditions in the neighbourhood of the magnetic structure via magneto-seismology (MS). We aim to reveal properties of the chromosphere/Transition Region above the sunspot penumbra using this technique. Hinode observed a sunspot as it was crossing the limb, providing a unique side on view of the sunspot atmosphere. The presence of large spicule-like jets is evident in \ion{Ca}{II} H images. The jets are found to support transverse wave motions that displace the central axis, which can be interpreted as a kink wave. The properties of a wave event are measured and used to determine the magnetic and density ... [READ MORE]

Authors: R J Morton
Projects: Hinode/SOT

Publication Status: Accepted A&A
Last Modified: 2014-05-14 13:09
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On the Nature and Genesis of EUV Waves: A Synthesis of Observations from SOHO, STEREO, SDO, and Hinode (Invited Review)   

Spiros Patsourakos   Submitted: 2012-05-19 01:29

A major, albeit serendipitous, discovery of the SOlar and Heliospheric Observatory mission was the observation by the Extreme Ultraviolet Telescope (EIT) of large-scale extreme ultraviolet (EUV) intensity fronts propagating over a significant fraction of the Sun's surface. These so-called EIT or EUV waves are associated with eruptive phenomena and have been studied intensely. However, their wave nature has been challenged by non-wave (or pseudo-wave) interpretations and the subject remains under debate. A string of recent solar missions has provided a wealth of detailed EUV observations of these waves bringing us closer to resolving the question of their nature. With this review, we gather the current state-of-the-art knowledge in the field and synthesize it into a picture of an EUV wave ... [READ MORE]

Authors: S. Patsourakos, A. Vourlidas
Projects: None

Publication Status: Solar Physics, 2012, On-line first
Last Modified: 2012-05-20 08:22
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The Inconvenient Truth About Coronal Dimmings   

Scott McIntosh   Submitted: 2008-11-24 13:46

We investigate the occurrence of a CME-driven coronal dimming using unique high resolution spectral images of the corona from the Hinode spacecraft. Over the course of the dimming event we observe the dynamic increase of non-thermal line broadening in the 195.12? emission line of Fe XII as the corona opens. As the corona begins to close, refill and brighten, we see a reduction of the non-thermal broadening towards the pre-eruption level. We propose that the dynamic evolution of non-thermal broadening is the result of the growth of Alfven wave amplitudes in the magnetically open rarefied dimming region, compared to the dense closed corona prior to the CME. We suggest, based on this proposition, that, as open magnetic regions, coronal dimmings must act just as coronal holes and be sources ... [READ MORE]

Authors: Scott W. McIntosh
Projects: Hinode/EIS

Publication Status: Submitted ApJ - rerouted to ApJL
Last Modified: 2008-11-25 05:50
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Subject will be restored when possible   

Stephane Regnier   Submitted: 2008-05-09 04:43

With the recent launch of the Hinode satellite our view of the nature and evolution of quiet-Sun regions has been improved. In light of the new high resolution observations, we revisit the study of the quiet Sun's topological nature. Topology is a tool to explain the complexity of the magnetic field, the occurrence of reconnection processes, and the heating of the corona. This Letter aims to give new insights to these different topics. Using a high-resolution Hinode/SOT observation of the line-of-sight magnetic field on the photosphere, we calculate the three dimensional magnetic field in the region above assuming a potential field. From the 3D field, we determine the existence of null points in the magnetic configuration.} From this model of a continuous field, we find that the ... [READ MORE]

Authors: S. Regnier, C. E. Parnell, A. L. Haynes
Projects: Hinode/SOT

Publication Status: Accepted in A&A Letter
Last Modified: 2008-09-23 21:02
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Subject will be restored when possible   

Charles M Brown   Submitted: 2007-09-11 17:31

A wavelength calibration of solar lines observed by the high resolution EUV Imaging Spectrometer (EIS) on the Hinode satellite is reported. Spectral features of the quiet sun and of two mildly active areas were measured and calibrated. A listing of the stronger observed lines with identi?cation of the leading contributor ions is presented. 41 lines are reported, with 90% identi?ed. Wavelength precisions (2?) of ?0:0031 ?A for the EIS short band and ?0:0029 ?A for the EIS long band are obtained. These lines, typical of 1?2?106 K plasmas, are recommended as standards for the establishment of EIS wavelength scales. The temperature of EIS varies by about 1:5? C around the orbit and also with spacecraft pointing. The correlation of these temperature changes with wavelength versus pixel ... [READ MORE]

Authors: .? C. M. Brown, H. Hara, S. Kamio, U. Feldman, J. F. Seely, G. A. Doschek, J. T. Mariska, C. M. Korendyke, J. Lang, K. Dere, J. L. Culhane, R. J. Thomas, and J. M. Davila
Projects: Hinode

Publication Status: PASJ October 2007, accepted
Last Modified: 2007-09-12 06:36
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A Critical Assessment of Nonlinear Force-Free Field Modeling of the Solar Corona for Active Region 10953   

Marc DeRosa   Submitted: 2009-02-05 19:26

Nonlinear force-free field (NLFFF) models are thought to be viable tools for investigating the structure, dynamics and evolution of the coronae of solar active regions. In a series of NLFFF modeling studies, we have found that NLFFF models are successful in application to analytic test cases, and relatively successful when applied to numerically constructed Sun-like test cases, but they are less successful in application to real solar data. Different NLFFF models have been found to have markedly different field line configurations and to provide widely varying estimates of the magnetic free energy in the coronal volume, when applied to solar data. NLFFF models require consistent, force- free vector magnetic boundary data. However, vector magnetogram ... [READ MORE]

Authors: Marc L. DeRosa, Carolus J. Schrijver, Graham Barnes, K. D. Leka, Bruce W. Lites, Markus J. Aschwanden, Tahar Amari, Aurelien Canou, James M. McTiernan, Stephane Regnier, Julia K. Thalmann, Gherardo Valori, Michael S. Wheatland, Thomas Wiegelmann, Mark C. M. Cheung, Paul A. Conlon, Marcel Fuhrmann, Bernd Inhester, Tilaye Tadesse
Projects: Hinode/SOT

Publication Status: ApJ (2009) 696 1780
Last Modified: 2015-08-21 23:30
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Measurements of non-thermal line widths in solar active regions   

David Brooks   Submitted: 2016-09-02 00:54

Spectral line widths are often observed to be larger than can be accounted for by thermal and instrumental broadening alone. This excess broadening is a key observational constraint for both nanoflare and wave dissipation models of coronal heating. Here we present a survey of non-thermal velocities measured in the high temperature loops (1-4 MK) often found in the cores of solar active regions. This survey of Hinode Extreme Ultraviolet Imaging Spectrometer (EIS) observations covers 15 non-flaring active regions that span a wide range of solar conditions. We find relatively small non-thermal velocities, with a mean value of 17.6 ? 5.3 km/s, and no significant trend with temperature or active region magnetic flux. These measurements appear to be inconsistent with those expected from ... [READ MORE]

Authors: Brooks, David H.; Warren, Harry P.
Projects: Hinode/EIS

Publication Status: ApJ, 820, 63 (2016)
Last Modified: 2016-09-07 12:14
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Dynamics and plasma properties of an X-ray jet from SUMER, EIS, XRT and EUVI A & B simultaneous observations   

Madjarska Maria   Submitted: 2010-08-05 04:44

Context. Small-scale transient phenomena in the quiet Sun are believed to play an important role in coronal heating and solar wind generation. One of them named as ?X-ray jet? is the subject of our study. Aims. We indent to investigate the dynamics, evolution and physical properties of this phenomenon. Methods. We combine spatially and temporally multi-instrument observations obtained simultaneously with the SUMER spectrometer onboard SoHO, EIS and XRT onboard Hinode, and EUVI/SECCHI onboard the Ahead and Behind STEREO spacecrafts. We derive plasma parameters such as temperatures and densities as well as dynamics by using spectral lines formed in the temperature range from 10 000 K to 12 MK. We also use image difference technique to investigate the evolution of the complex structure of ... [READ MORE]

Authors: M.S. Madjarska
Projects: Hinode/EIS,Hinode/XRT,SoHO-SUMER,STEREO

Publication Status: submitted to A&A
Last Modified: 2010-08-05 07:16
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Temperature Tomography of a Coronal Sigmoid Supporting the Gradual Formation of a Flux Rope   

Durgesh Tripathi   Submitted: 2009-04-30 04:54

Multi-wavelength observations of a sigmoidal (S-shaped) solar coronal source by the EUV Imaging Spectrometer and the X-ray Telescope aboard the Hinode spacecraft and by the EUV Imager aboard STEREO are reported. The data reveal the coexistence of a pair of J-shaped hot arcs at temperatures T>2 MK with an S-shaped structure at somewhat lower temperatures T~1.3 MK. The middle section of the S-shaped structure runs along the polarity inversion line of the photospheric field, bridging the gap between the arcs. Flux cancellation occurs at the same location in the photosphere. The sigmoid forms in the gradual decay phase of the active region, which does not experience an eruption. These findings correspond to the expected signatures of a flux rope forming, or being augmented, gradually by a ... [READ MORE]

Authors: Durgesh Tripathi, Bernhard Kliem, Helen Mason, Peter Young, Lucie Green
Projects: Hinode/EIS,Hinode/XRT,SoHO-MDI,STEREO

Publication Status: Accepted for Publication in ApJ Letters
Last Modified: 2009-04-30 08:41
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Modeling Active Region Transient Brightenings Observed with X-Ray Telescope as Multi-stranded Loops   

Adam Kobelski   Submitted: 2014-08-22 18:16

Strong evidence exists that coronal loops as observed in extreme ultraviolet and soft X-rays may not be monolithic isotropic structures, but can often be more accurately modeled as bundles of independent strands. Modeling the observed active region transient brightenings (ARTBs) within this framework allows for the exploration of the energetic ramifications and characteristics of these stratified structures. Here we present a simple method of detecting and modeling ARTBs observed with the Hinode X-Ray Telescope (XRT) as groups of zero-dimensional strands, which allows us to probe parameter space to better understand the spatial and temporal dependence of strand heating in impulsively heated loops. This partially automated method can be used to analyze a large number of observations to ... [READ MORE]

Authors: Adam R. Kobelski, David E. McKenzie, Martin Donachie
Projects: Hinode/XRT

Publication Status: ApJ (Accepted)
Last Modified: 2014-08-27 12:58
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Non-Linear Force-Free Modeling of a Long-Lasting Coronal Sigmoid   

Antonia Savcheva   Submitted: 2009-09-04 10:27

A study of the magnetic configuration and evolution of a long-lasting quiescent coronal sigmoid is presented. The sigmoid was observed by {it Hinode}/XRT and TRACE between 2007 Feb 6 and Feb 12 when it finally erupted. We construct non-linear force-free field models for several observations during this period, using the flux rope insertion method. The high spatial and temporal resolution of XRT allows us to finely select best-fit models that match the observations. The modeling shows that a highly sheared field, consisting of a weakly twisted flux rope inbedded in a potential field, very well describes the structure of the X-ray sigmoid. The flux rope reaches a stable equilibrium, but its axial flux is close to the stability limit of about $5 imes 10^{20}$ Mx. The ... [READ MORE]

Authors: Antonia Savcheva and Adrian van Ballegooijen
Projects: Hinode/XRT

Publication Status: accepted
Last Modified: 2009-09-04 14:38
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Magnetic Flux Rope Shredding by a Hyperbolic Flux Tube: The Detrimental Effects of Magnetic Topology on Solar Eruptions   

Georgios Chintzoglou   Submitted: 2017-07-11 12:59

We present the analysis of an unusual failed eruption captured in high cadence and in many wavelengths during the observing campaign in support of the VAULT2.0 sounding rocket launch. The refurbished Very high Angular resolution Ultraviolet Telescope (VAULT2.0) is a Lyα (λ 1216 {\AA}) spectroheliograph launched on September 30, 2014. The campaign targeted active region NOAA AR 12172 and was closely coordinated with the Hinode and IRIS missions and several ground-based observatories (NSO/IBIS, SOLIS, and BBSO). A filament eruption accompanied by a low level flaring event (at the GOES C-class level) occurred around the VAULT2.0 launch. No Coronal Mass Ejection (CME) was observed. The eruption and its source region, however, were recorded by the campaign instruments in many ... [READ MORE]

Authors: Georgios Chintzoglou, Angelos Vourlidas, Antonia Savcheva, Svetlin Tassev, Samuel Tun Beltran, Guillermo Stenborg
Projects: GOES X-rays,Hinode/SOT,IRIS,SDO-AIA,SDO-HMI,SoHO-LASCO,Very high-Angular resolution Ultraviolet Telescope 2.0 (VAULT2)

Publication Status: Published in the Astrophysical Journal, Vol 843, p. 93
Last Modified: 2017-07-12 11:41
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Subject will be restored when possible   

Stephane Regnier   Submitted: 2008-05-09 04:44

With the recent launch of the Hinode satellite our view of the nature and evolution of quiet-Sun regions has been improved. In light of the new high resolution observations, we revisit the study of the quiet Sun's topological nature. Topology is a tool to explain the complexity of the magnetic field, the occurrence of reconnection processes, and the heating of the corona. This Letter aims to give new insights to these different topics. Using a high-resolution Hinode/SOT observation of the line-of-sight magnetic field on the photosphere, we calculate the three dimensional magnetic field in the region above assuming a potential field. From the 3D field, we determine the existence of null points in the magnetic configuration.} From this model of a continuous field, we find that the ... [READ MORE]

Authors: S. Regnier, C. E. Parnell, A. L. Haynes
Projects: Hinode/SOT

Publication Status: Accepted in A&A Letter
Last Modified: 2008-09-23 21:02
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FIP Bias Evolution in a Decaying Active Region   

Deb Baker   Submitted: 2015-01-30 02:59

Solar coronal plasma composition is typically characterized by first ionization potential (FIP) bias. Using spectra obtained by Hinode's EUV Imaging Spectrometer (EIS) instrument, we present a series of large-scale, spatially resolved composition maps of active region (AR) 11389. The composition maps show how FIP bias evolves within the decaying AR from 2012 January 4-6. Globally, FIP bias decreases throughout the AR. We analyzed areas of significant plasma composition changes within the decaying AR and found that small-scale evolution in the photospheric magnetic field is closely linked to the FIP bias evolution observed in the corona. During the AR's decay phase, small bipoles emerging within supergranular cells reconnect with the pre-existing AR field, creating a pathway along which ... [READ MORE]

Authors: D. Baker, D. H. Brooks, P. D?moulin, S. L. Yardley, L. van Driel-Gesztelyi, D. M. Long, L. M. Green
Projects: Hinode/EIS

Publication Status: Accepted ApJ
Last Modified: 2015-02-03 10:59
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Non-potential field formation in the X-shaped quadrupole magnetic field configuration   

Yusuke Kawabata   Submitted: 2017-06-11 19:16

Some types of solar flares are observed in X-shaped quadrupolar field configuration. To understand the magnetic energy storage in such a region, we studied non-potential field formation in an X-shaped quadrupolar field region formed in the active region NOAA 11967, which produced three X-shaped M-class flares on February 2, 2014. Nonlinear force-free field modeling was applied to a time series of vector magnetic field maps from the Solar Optical Telescope on board Hinode and Helioseismic and Magnetic Imager on board Solar Dynamics Observatory. Our analysis of the temporal three-dimensional magnetic field evolution shows that the sufficient free energy had already been stored more than 10 hours before the occurrence of the first M-class flare and that the storage was observed in a ... [READ MORE]

Authors: Kawabata, Yusuke; Inoue, Satoshi; Shimizu, Toshifumi
Projects: Hinode/SOT

Publication Status: Accepted for publication in ApJ
Last Modified: 2017-06-14 10:03
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The Role of Magnetic Topology in the Heating of Active Region Coronal Loops   

Jin-Yi Lee   Submitted: 2010-09-09 09:13

We investigate the evolution of coronal loop emission in the context of the coronal magnetic field topology. New modeling techniques allow us to investigate the magnetic field structure and energy release in active regions. Using these models and high resolution multi-wavelength coronal observations from the Transition Region and Coronal Explorer (TRACE) and the X-ray Telescope (XRT) on Hinode, we are able to establish a relationship between the light curves of coronal loops and their associated magnetic topologies for NOAA Active Region 10963. We examine loops that show both transient and steady emission, and we find that loops that show many transient brightenings are located in domains associated with a high number of separators. This topology provides an environment for continual ... [READ MORE]

Authors: J.-Y. Lee, Graham Barnes, K. D. Leka, Katharine Reeves, Kelly Korreck, Leon Golub, and E. E. DeLuca
Projects: Hinode/XRT

Publication Status: Accepted for publication in ApJ
Last Modified: 2010-09-10 13:12
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A single picture for solar coronal outflows and radio noise storms   

Guillaume Aulanier   Submitted: 2010-09-28 03:22

We propose a unified interpretation for persistent coronal outflows and metric radio noise storms, two phenomena typically observed in association with quiescent solar active regions. Our interpretation is based on multi-wavelength observations of two such regions as they crossed the meridian in May and July 2007. For both regions, we observe a persistent pattern of blue-shifted coronal emission in high-temperature lines with Hinode/EIS, and a radio noise storm with the Nanc?ay Radioheliograph. The observations are supplemented by potential and linear force-free extrapolations of the photospheric magnetic field over large computational boxes, and by a detailed analysis of the coronal magnetic field topology. We find true separatrices in the coronal field and null points high in ... [READ MORE]

Authors: Del Zanna, G., Aulanier, G., Klein, K.-L., Torok, T.
Projects: Hinode/EIS,Hinode/SOT,Hinode/XRT,SoHO-MDI

Publication Status: A&A (accepted)
Last Modified: 2010-09-28 09:31
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Cristina Chifor   Submitted: 2008-01-14 08:22

Aims: We study the physical properties of an active region (AR) jet in order to probe the mechanisms responsible for it. Methods: We report 2007 January 15/16 observations of a recurring jet situated on the west side of NOAA AR 10938. Multi-wavelength data from all three instruments onboard Hinode were analysed. This paper focuses on one instance of a jet observed with the Hinode/EUV Imaging Spectrometer (EIS). Using EIS raster data we measured the temperatures, Doppler shifts, density, and filling factor. Results: A strong blue-shifted component and an indication of a weak red-shifted component at the base of the jet was observed around Log T_e= 6.2. The up-flow velocities exceeded 150 km/s. The jet component was seen over a range of temperatures between 5.4 and 6.4 in Log T_e. Using ... [READ MORE]

Authors: C. Chifor, P. R. Young, H. Isobe, H. E. Mason, D. Tripathi, H. Hara, T. Yokoyama
Projects: Hinode/EIS,Hinode/SOT,Hinode/XRT

Publication Status: A&A Letters (Hinode special edition) , in press
Last Modified: 2008-01-14 08:47
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Statistical Study on the Nature of Solar Flux Emergence   

Kenichi Otsuji   Submitted: 2011-06-12 20:09

We studied 101 flux emergence events ranging from small ephemeral regions to large emerging flux regions which were observed with Hinode Solar Optical Telescope filtergram. We investigated how the total magnetic flux of the emergence event controls the nature of emergence. To determine the modes of emergences, horizontal velocity fields of global motion of the magnetic patches in the flux emerging sites were measured by the local correlation tracking. Between two main polarities of the large emerging flux regions with more than around 2 imes 10^19 Mx, there were the converging flows of anti-polarity magnetic patches. On the other hand, small ephemeral regions showed no converging flow but simple diverging pattern. When we looked into the detailed features in the emerging sites, ... [READ MORE]

Authors: Kenichi Otsuji, Reizaburo Kitai, Kiyoshi Ichimoto, Kazunari Shibata
Projects: Hinode/SOT,SoHO-MDI

Publication Status: Accepted
Last Modified: 2011-06-14 19:51
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David E. McKenzie   Submitted: 2008-01-16 14:58

Aims: Coronal sigmoids are important sources of eruptions into interplanetary space, and a handful of models have been proposed to explain their characteristic S shape. However, the coronal X-ray images available to date have generally not had sufficient resolution to distinguish between these models. The goal of the present investigation is to determine whether the new observations from Hinode can help us to make such a distinction. Methods: We present the first observations of a persistent coronal sigmoid obtained with the Hinode X-Ray Telescope (XRT). The excellent angular resolution of XRT (1 arcsecond per pixel) and the sigmoid's location near disk center combined to provide an unprecedented view of the formation and eruption of this phenomenon. We compared the observed ... [READ MORE]

Authors: McKenzie, David E., & Canfield, Richard C.
Projects: Hinode/XRT,SoHO-MDI

Publication Status: A&A Letters (accepted, in press)
Last Modified: 2008-01-17 08:21
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Structure of prominence legs: Plasma and magnetic field   

Peter James Levens   Submitted: 2015-12-17 07:04

We investigate the properties of a `solar tornado' observed on 15 July 2014, and aim to link the behaviour of the plasma to the internal magnetic field structure of the associated prominence. We made multi-wavelength observations with high spatial resolution and high cadence using the SDO/AIA, the IRIS spectrograph and the Hinode/SOT instrument. Along with spectropolarimetry provided by the THEMIS telescope we have coverage of both optically thick emission lines and magnetic field information. AIA reveals that the two legs of the prominence are strongly absorbing structures which look like they are rotating, or oscillating in the plane of the sky. The two prominence legs, which are both very bright in Ca II (SOT), are not visible in the IRIS Mg II slit-jaw images. This is explained by the ... [READ MORE]

Authors: Peter Levens, Brigitte Schmieder, Nicolas Labrosse, Arturo Lopez Ariste
Projects: Hinode/SOT,IRIS,SDO-AIA,THEMIS/MTR

Publication Status: ApJ accepted, article in pre-print
Last Modified: 2015-12-19 16:44
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Hui Li   Submitted: 2007-09-16 23:18

In this paper, we use optical and X-ray data from the Hinode satellite to study the response of solar chromosphere and corona to the emerging flux in the photosphere. Totally twelve emerging flux regions (EFRs) are selected to conduct this study. The average separation of the two polarities and lifetime of these EFRs are 3.2'' and 40 min, respectively. All these regions show corresponding enhanced emission in Ca II H line and soft X-rays (SXR) with different filters, indicating that these small-scale and short-lived EFRs heat the chromosphere and the corona to some extent.

Authors: H. Li, T. Sakurai, K. Ichimito, Y. Suematsu, S. Tsuneta, Y. Katsukawa, et al.
Projects: Hinode

Publication Status: PASJ, Vol. 59, Hinode Special Issue (accepted)
Last Modified: 2007-09-17 08:12
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Chromospheric jets around the edges of sunspots   

Richard Morton   Submitted: 2012-05-11 02:32

Evidence is beginning to be put forward that demonstrates the role of the chromosphere in supplying energy and mass to the corona. We aim to asses the role of chromospheric jets in active region dynamics}{Using a combination of the {Hinode/SOT} Ca II H and TRACE 1550 {AA} and 1600 {AA} filters we examine chromospheric jets situated at the edge of a sunspot.}{Analysis reveals a near continuous series of jets, that raise chromospheric material into the low corona above a sunspot. The jets have average rise speeds of 30 km,s^{-1} and a range of 10-100km,s^{-1}. Enhanced emission observed at the jets leading edge suggests the formation of a shock front. Increased emission in TRACE bandpasses above the sunspot and the disappearance of the jets from the Ca II filter suggests that some of the ... [READ MORE]

Authors: R. J. Morton
Projects: Hinode/SOT

Publication Status: In Press A&A
Last Modified: 2012-05-11 11:52
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Subject will be restored when possible   

Louise Harra   Submitted: 2007-09-11 08:21

Coronal dimming has been a signature used to determine the source of plasma that forms part of a coronal mass ejection (CME) for many years. Generally dimming is detected through imaging instruments such as SOHO EIT by taking difference images. Hinode tracked active region 10930 from which there were a series of flares. We combine dimming observations from EIT with Hinode data to show the impact of flares and coronal mass ejections on the region surrounding the flaring active region, and we discuss evidence that the eruption resulted in a prolonged steady outflow of material from the corona. The dimming region shows clear structure with extended loops whose footpoints are the source of the strongest outflow ($approx$ 40 km/s). This confirms that the loops that are disrupted ... [READ MORE]

Authors: Harra, Hara, Imada, Young, Williams, Sterling, Korendyke and Attrill
Projects: Hinode

Publication Status: PASJ, in press
Last Modified: 2007-09-12 06:36
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Hiroko Watanabe   Submitted: 2008-04-06 23:39

A high resolution imaging observation of a sunspot umbra was made with the Hinode Solar Optical Telescope. Filtergrams at wavelengths of the blue and green continua were taken during three consecutive days. The umbra consisted of a dark core region, several diffuse components, and numerous umbral dots. We derived basic properties of umbral dots (UDs), especially their temperatures, lifetimes, proper motions, spatial distribution, and morphological evolution. The brightness of UDs is confirmed to depend on the brightness of their surrounding background. Several UDs show fission and fusion. Thanks to the stable condition of the space observation, we could for the first time follow the temporal behavior of these events. The derived properties of the internal ... [READ MORE]

Authors: Reizaburo Kitai, Hiroko Watanabe, Tahei Nakamura, Ken-ichi Otsuji, Takuma Matsumoto, Satoru UeNo, Shin-ichi Nagata, Kazunari Shibata, Richard Muller, Kiyoshi Ichimoto, Saku Tsuneta, Yoshinori Suematsu, Yukio Katsukawa, Toshifumi Shimizu, Theodore D. Tarbell, Richard A. Shine, Alan M. Title, Bruce W. Lites
Projects: Hinode/SOT

Publication Status: Published in PASJ 59 No.SP3 (Hinode Special Issue)
Last Modified: 2008-09-23 21:11
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The Solar Source of a Magnetic Cloud Using a Velocity Difference Technique   

Louise Harra   Submitted: 2010-11-03 03:52

For large eruptions on the Sun, it is often a problem that the core dimming region cannot be observed due to the bright emission from the flare itself. However, spectroscopic data can provide the missing information through the measurement of Doppler velocities. In this paper we analyse the well-studied flare and coronal mass ejection that erupted on the Sun on 13 December 2006 and reached the Earth on 14 December 2006. In this example, although the imaging data were saturated at the flare site itself, we could extract information on the core dimming region through velocity measurements, as well as on the remote dimmings. The purpose of this paper is to determine more accurately the magnetic flux of the solar source region, potentially involved in the ejection, through a ... [READ MORE]

Authors: Harra, Mandrini, Dasso, Gulisano, Steed and Imada
Projects: Hinode/EIS

Publication Status: Solar Physics, accepted
Last Modified: 2010-11-03 08:53
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Jane Benedetta Noglik   Submitted: 2008-07-28 08:14

Active region 10961 was observed over a five day period (2007 July 2-6) by instrumentation on-board STEREO, Hinode, TRACE and SOHO. As it progressed from Sun centre to the solar limb a comprehensive analysis of the EUV, X-ray and magnetic field data reveals clearly observable changes in the global nature of the region. Temperature analyses undertaken using STEREO EUVI double filter ratios and XRT single and combined filter ratios demonstrate an overall cooling of the region from between 1.6 - 3.0~MK to 1.0 - 2.0~MK over the five days. Similarly, Hinode EIS density measurements show a corresponding increase in density of 27~$\%$. Moss, cool (1~MK) outer loop areas and hotter core loop regions were examined and compared with potential magnetic field extrapolations from SOHO MDI ... [READ MORE]

Authors: Jane B. Noglik, Robert W. Walsh & Rhona C. Maclean
Projects: Hinode/EIS,Hinode/XRT,SoHO-MDI,STEREO,TRACE

Publication Status: Submitted to ApJ
Last Modified: 2008-09-23 20:53
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Magnetic Reconnection along Quasi-Separatrix Layers as a Driver of Ubiquitous Active Region Outflows   

Deborah Baker   Submitted: 2009-09-25 07:01

Hinode's EUV Imaging Spectrometer (EIS) has discovered ubiquitous outflows of a few to 50 km/sec from active regions (ARs). These outflows are most prominent at the AR boundary and appear over monopolar magnetic areas. They are linked to strong non-thermal line broadening and are stronger in hotter EUV lines. The outflows persist for at least several days. Using Hinode EIS and X-Ray Telescope observations of AR 10942 coupled with magnetic modeling, we demonstrate that the outflows originate from specific locations of the magnetic topology where field lines display strong gradients of magnetic connectivity, namely quasi-separatrix layers (QSLs), or in the limit of infinitely thin QSLs, separatrices. We found the strongest AR outflows to be in the vicinity of QSL sections located over ... [READ MORE]

Authors: D. Baker, L. van Driel-Gesztelyi, C. H. Mandrini, P. Demoulin, M. J. Murray
Projects: Hinode/EIS

Publication Status: ApJ (accepted)
Last Modified: 2009-09-25 08:08
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Response of the Solar Atmosphere to the Emergence of ?Serpentine? Magnetic Field   

Louise Harra   Submitted: 2010-04-26 06:58

Active region magnetic flux that emerges to the photosphere from below will show complexity in the structure, with many small-scale fragmented features appearing in between the main bipole and then disappearing. Some fragments seen will be absorbed into the main polarities and others seem to cancel with opposite magnetic field. In this paper we investigate the response of the corona to the behaviour of these small fragments and whether energy through reconnection will be transported into the corona. In order to investigate this we analyse data from the Hinode space mission during flux emergence on 1 ? 2 December 2006. At the initial stages of flux emergence several small-scale enhancements (of only a few pixels size) are seen in the coronal line widths and diffuse coronal ... [READ MORE]

Authors: L. K. Harra, T. Magara, H. Hara, S. Tsuneta, T. J. Okamoto and A. J. Wallace
Projects: Hinode/EIS

Publication Status: in press
Last Modified: 2010-04-26 09:12
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Spicule Dynamics over Plage Region   

Tetsu Anan   Submitted: 2010-02-11 01:36

We studied spicular jets over a plage area and derived their dynamic characteristics using Hinode Solar Optical Telescope (SOT) high-resolution images. The target plage region was near the west limb of the solar disk. This location permitted us to study the dynamics of spicular jets without the overlapping effect of spicular structures along the line of sight. In this work, to increase the ease with which we can identify spicules on the disk, we applied the image processing method `MadMax' developed by Koutchmy et al. (1989). It enhances fine, slender structures (like jets), over a diffuse background. We identified 169 spicules over the target plage. This sample permits us to derive statistically reliable results regarding spicular dynamics. The properties of plage spicules can be ... [READ MORE]

Authors: Tetsu Anan, Reizaburo Kitai, Tomoko Kawate, Takuma Matsumoto, Kiyoshi Ichimoto, Kazunari Shibata, Andrew Hillier, Kenichi Otsuji, Hiroko Watanabe, Satoru UeNo, Shin'ichi Nagata, Takako T.Ishii, Hiroyuki Komori, Keisuke Nishida, Tahei Nakamura, Hiroaki Isobe, Masaoki Hagino
Projects: Hinode/SOT

Publication Status: PASJ (accepted)
Last Modified: 2010-02-11 13:34
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Implications of X-ray Observations for Electron Acceleration and Propagation in Solar Flares  

Amir Caspi   Submitted: 2011-10-28 12:16

High-energy X-rays and gamma-rays from solar flares were discovered just over fifty years ago. Since that time, the standard for the interpretation of spatially integrated flare X-ray spectra at energies above several tens of keV has been the collisional thick-target model. After the launch of the Reuven Ramaty High Energy Solar Spectroscopic Imager (RHESSI) in early 2002, X-ray spectra and images have been of sufficient quality to allow a greater focus on the energetic electrons responsible for the X-ray emission, including their origin and their interactions with the flare plasma and magnetic field. The result has been new insights into the flaring process, as well as more quantitative models for both electron acceleration and propagation, and for the flare environment with which the ... [READ MORE]

Authors: Gordon D. Holman, Markus J. Aschwanden, Henry Aurass, Marina Battaglia, Paolo C. Grigis, Eduard P. Kontar, Wei Liu, Pascal Saint-Hilaire, Valentina V. Zharkova
Projects: GONG,Hinode/EIS,Hinode/SOT,Hinode/XRT,Nobeyama Radioheliograph,Owens Valley Solar Array,RHESSI,SDO-AIA,SDO-HMI,SDO-EVE,SoHO-EIT,SoHO-MDI,SoHO-CDS,SoHO-LASCO,SoHO-SUMER,STEREO,TRACE

Publication Status: Published -- Holman, G. D., et al. 2011, Space Sci. Rev., 159, 107; DOI 10.1007/s11214-010-9680-9
Last Modified: 2011-11-17 14:18
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LYRA observations of two oscillation modes in a single flare  

Tom Van Doorsselaere   Submitted: 2011-08-23 06:43

This abstract was corrupted following database problems and is being recovered. It will be restored as quickly as possible. Any questions, please send them to Alisdair. Sorry for any incovenience.


Authors: Van Doorsselaere T., De Groof A., Zender J., Berghmans D., and Goossens M.
Projects: Hinode/XRT, PROBA2/LYRA

Publication Status: ApJ (accepted)
Last Modified: 2011-08-23 08:55
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Deducing Electron Properties From Hard X-Ray Observations  

Amir Caspi   Submitted: 2011-10-28 12:22

X-radiation from energetic electrons is the prime diagnostic of flare-accelerated electrons. The observed X-ray flux (and polarization state) is fundamentally a convolution of the cross-section for the hard X-ray emission process(es) in question with the electron distribution function, which is in turn a function of energy, direction, spatial location and time. To address the problems of particle propagation and acceleration one needs to infer as much information as possible on this electron distribution function, through a deconvolution of this fundamental relationship. This review presents recent progress toward this goal using spectroscopic, imaging and polarization measurements, primarily from the Reuven Ramaty High Energy Solar Spectroscopic Imager (RHESSI). Previous conclusions ... [READ MORE]

Authors: E.P. Kontar, J.C. Brown, A.G. Emslie, W. Hajdas, G.D. Holman, G. J. Hurford, J. Kasparova, P. C. V. Mallik, A. M. Massone, M. L. McConnell, M. Piana, M. Prato, E. J. Schmahl, E. Suarez-Garcia
Projects: GONG,Hinode/EIS,Hinode/SOT,Hinode/XRT,Nobeyama Radioheliograph,Owens Valley Solar Array,RHESSI,SDO-AIA,SDO-HMI,SDO-EVE,SoHO-EIT,SoHO-MDI,SoHO-CDS,SoHO-LASCO,SoHO-SUMER,STEREO,TRACE

Publication Status: Published -- Kontar, E. P., et al. 2011, Space Sci. Rev., 159, 301; DOI 10.1007/s11214-011-9804-x
Last Modified: 2011-11-17 14:20
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Sigmoidal Active Region on the Sun: Comparison of a Magnetohydrodynamical Simulation and a Non-Linear Force-Free Field Mode  

Antonia Savcheva   Submitted: 2012-03-05 12:44

In this paper we show that when accurate non-linear force free field (NLFFF) models are analyzed together with high resolution magnetohydrodynamic (MHD) simulations, we can determine the physical causes for the CME eruption on 12-Feb-2007. We compare the geometrical and topological properties of the three-dimensional magnetic fields given by both methods in their pre-eruptive phases. We arrive at a consistent picture for the evolution and eruption of the sigmoid. Both the MHD simulation and the observed magnetic field evolution show that flux cancellation plays an important role in building the flux rope. We compute the squashing factor, Q, in different horizontal maps in the domains. The main shape of the quasi-separatrix layers (QSLs), are very similar between the NLFFF and MHD models. ... [READ MORE]

Authors: A. Savcheva, E. Pariat, A. van Ballegooijen, G. Aulanier, E. DeLuca
Projects: Hinode/XRT

Publication Status: accepted
Last Modified: 2012-03-05 14:19
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Combined Modeling of Acceleration, Transport, and Hydrodynamic Response in Solar Flares: I. The Numerical Model  

Wei Liu   Submitted: 2009-06-13 00:52

Acceleration and transport of high-energy particles and fluid dynamics of atmospheric plasma are interrelated aspects of solar flares, but they were artificially separated for simplicity in the past. We present here self-consistently combined Fokker-Planck modeling of particles and hydrodynamic simulation of flare plasma. Energetic electrons are modeled with the Stanford unified code of acceleration, transport, and radiation, while plasma is modeled with the NRL flux tube code. We calculated the collisional heating rate from the particle transport code, which is more accurate than those based on approximate analytical solutions. We used a realistic spectrum of injected electrons provided by the stochastic acceleration model, which has a smooth transition from a quasi-thermal background at ... [READ MORE]

Authors: Wei Liu, Vahe Petrosian, and John T. Mariska
Projects: Hinode/SOT,RHESSI

Publication Status: ApJ (2009 September 10, vol 702, p. 1553-1566, online first August 24)
Last Modified: 2009-08-24 10:32
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Spatially and Spectrally Resolved Observations of a Zebra Pattern in Solar Decimetric Radio Burst  

Bin Chen   Submitted: 2011-05-03 20:33

We present the first interferometric observation of a zebra-pattern radio burst with simultaneous high spectral (~ 1 MHz) and high time (20 ms) resolution. The Frequency-Agile Solar Radiotelescope (FASR) Subsystem Testbed (FST) and the Owens Valley Solar Array (OVSA) were used in parallel to observe the X1.5 flare on 14 December 2006. By using OVSA to calibrate the FST the source position of the zebra pattern can be located on the solar disk. With the help of multi-wavelength observations and a nonlinear force-free field (NLFFF) extrapolation, the zebra source is explored in relation to the magnetic field configuration. New constraints are placed on the source size and position as a function of frequency and time. We conclude that the zebra burst is consistent with a double-plasma ... [READ MORE]

Authors: Bin Chen, Timothy S. Bastian, Dale E. Gary, Ju Jing
Projects: Hinode/SOT,Hinode/XRT,Owens Valley Solar Array

Publication Status: Accepted for publication in ApJ
Last Modified: 2011-05-11 12:15
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Oscillations and waves in solar spicules  

Teimuraz Zaqarashvili   Submitted: 2009-06-10 05:38

Since their discovery, spicules have attracted increased attention as energy/mass bridges between the dense and dynamic photosphere and the tenuous hot solar corona. Mechanical energy of photospheric random and coherent motions can be guided by magnetic field lines, spanning from the interior to the upper parts of the solar atmosphere, in the form of waves and oscillations. Since spicules are one of the most pronounced features of the chromosphere, the energy transport they participate in can be traced by the observations of their oscillatory motions. Oscillations in spicules have been observed for a long time. However the recent high-resolutions and high cadence space and ground based facilities with superb spatial, temporal and spectral capacities brought new aspects in the research of ... [READ MORE]

Authors: Zaqarashvili, T.V. and Erdelyi, R.
Projects: Hinode/SOT

Publication Status: Space Science Reviews (accepted)
Last Modified: 2009-06-10 09:18
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Detection and Interpretation Of Long-Lived X-Ray Quasi-Periodic Pulsations in the X-Class Solar Flare On 2013 May 14  

Brian Dennis   Submitted: 2017-06-13 16:25

Quasi-periodic pulsations (QPP) seen in the time derivative of the GOES soft X-ray light curves are analyzed for the near-limb X3.2 event on 14 May 2013. The pulsations are apparent for a total of at least two hours from the impulsive phase to well into the decay phase, with a total of 163 distinct pulses evident to the naked eye. A wavelet analysis shows that the characteristic time scale of these pulsations increases systematically from ~25 s at 01:10 UT, the time of the GOES peak, to ~100 s at 02:00 UT. A second ridge in the wavelet power spectrum, most likely associated with flaring emission from a different active region, shows an increase from ~40 s at 01:40 UT to ~100 s at 03:10 UT. We assume that the QPP that produced the first ridge result from vertical kink-mode oscillations of ... [READ MORE]

Authors: Brian R. Dennis, Anne K. Tolbert, Andrew Inglis, Jack Ireland, Tongjiang Wang, Gordon D. Holman, Laura A. Hayes, and Peter T. Gallagher
Projects: GOES X-rays,Hinode/XRT,RHESSI,SDO-AIA,SDO-EVE

Publication Status: Published in ApJ, 834:84, 2017
Last Modified: 2017-06-14 10:01
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What is the true nature of blinkers  

Maria Madjarska   Submitted: 2011-11-07 07:03

This abstract was corrupted following database problems and is being recovered. It will be restored as quickly as possible. Any questions, please send them to Alisdair. Sorry for any incovenience.


Authors: S. Subramanian, M. S. Madjarska, J. G. Doyle and D. Bewsher
Projects: Hinode/EIS,Hinode/SOT,Hinode/XRT,SoHO-CDS,STEREO

Publication Status: in press in A&A
Last Modified: 2011-11-07 10:47
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Subject will be restored when possible  

Thomas Wiegelmann   Submitted: 2008-01-08 08:10

The solar magnetic field is key to understanding the physical processes in the solar atmosphere. Nonlinear force-free codes have been shown to be useful in extrapolating the coronal field upward from underlying vector boundary data. However, we can only measure the magnetic field vector routinely with high accuracy in the photosphere, and unfortunately these data do not fulfill the force-free condition. We must therefore apply some transformations to these data before nonlinear force-free extrapolation codes can be self-consistently applied. To this end, we have developed a minimization procedure that yields a more chromosphere-like field, using the measured photospheric field vectors as input. The procedure includes force-free consistency integrals, spatial smoothing, and ... [READ MORE]

Authors: Wiegelmann, T; Thalmann, J.K.; Schrijver, C.J.; DeRosa, M.L.; Metcalf, T.R.
Projects: Hinode/SOT

Publication Status: Solar Physics, accepted
Last Modified: 2008-01-08 09:53
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An Observational Overview of Solar Flares  

Amir Caspi   Submitted: 2011-10-28 12:15

We present an overview of solar flares and associated phenomena, drawing upon a wide range of observational data primarily from the RHESSI era. Following an introductory discussion and overview of the status of observational capabilities, the article is split into topical sections which deal with different areas of flare phenomena (footpoints and ribbons, coronal sources, relationship to coronal mass ejections) and their interconnections. We also discuss flare soft X-ray spectroscopy and the energetics of the process. The emphasis is to describe the observations from multiple points of view, while bearing in mind the models that link them to each other and to theory. The present theoretical and observational understanding of solar flares is far from complete, so we conclude with a brief ... [READ MORE]

Authors: Lyndsay Fletcher, Brian R. Dennis, Hugh S. Hudson, S?m Krucker, Ken Phillips, Astrid Veronig, Marina Battaglia, Laura Bone, Amir Caspi, Qingrong Chen, Peter Gallagher, Paolo C. Grigis, Haisheng Ji, Ryan O. Milligan, Manuela Temmer
Projects: GONG,Hinode/EIS,Hinode/SOT,Hinode/XRT,Nobeyama Radioheliograph,Owens Valley Solar Array,RHESSI,SDO-AIA,SDO-HMI,SDO-EVE,SoHO-EIT,SoHO-MDI,SoHO-CDS,SoHO-LASCO,SoHO-SUMER,STEREO,TRACE

Publication Status: Published -- Fletcher, L., et al. 2011, Space Sci. Rev., 159, 19; DOI 10.1007/s11214-010-9701-8
Last Modified: 2011-11-17 14:18
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Periodic spectral line asymmetries in solar coronal structures from slow magnetoacoustic waves  

Erwin Verwichte   Submitted: 2010-09-17 11:24

Recent spectral observations of upward moving quasi-periodic intensity perturbations in solar coronal structures have shown evidence of periodic line asymmetries near their footpoints. These observations challenge the established interpretation of the intensity perturbations in terms of propagating slow magnetoacoustic waves. We show that slow waves inherently have a bias towards enhancement of emission in the blue wing of the emission line due to in-phase behaviour of velocity and density perturbations. We demonstrate that slow waves cause line asymmetries when the emission line is averaged over an oscillation period or when a quasi-static plasma component in the line-of-sight is included. Therefore, we conclude that slow magnetoacoustic waves remain a valid explanation for the observed ... [READ MORE]

Authors: Verwichte, E., Marsh, M., Foullon, C., Van Doorsselaere, T., De Moortel, I., Hood, A.W. and Nakariakov, V.M.
Projects: Hinode/EIS

Publication Status: accepted for publication in ApJL
Last Modified: 2010-09-18 13:46
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Diagnosing the time-dependence of active region core heating from the emission measure: II. Nanoflare trains  

Stephen Bradshaw   Submitted: 2013-03-18 20:05

The time-dependence of heating in solar active regions can be studied by analyzing the slope of the emission measure distribution cool-ward of the peak. In a previous study we showed that low-frequency heating can account for 0\% to 77\% of active region core emission measures. We now turn our attention to heating by a finite succession of impulsive events for which the timescale between events on a single magnetic strand is shorter than the cooling timescale. We refer to this scenario as a ``nanoflare train'' and explore a parameter space of heating and coronal loop properties with a hydrodynamic model. Our conclusions are: (1) nanoflare trains are consistent with 86\% to 100\% of observed active region cores when uncertainties in the atomic data are properly accounted for; (2) steeper ... [READ MORE]

Authors: Jeffrey W. Reep, Stephen J. Bradshaw, James A. Klimchuk
Projects: Hinode/EIS

Publication Status: Published
Last Modified: 2013-03-19 09:40
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Forward Modelling of Standing Kink Modes in Coronal Loops I. Synthetic Views  

Ding Yuan   Submitted: 2016-03-08 03:32

Kink magnetohydrodynamic (MHD) waves are frequently observed in various magnetic structures of the solar atmosphere. They may contribute significantly to coronal heating and could be used as a tool to diagnose the solar plasma. In this study, we synthesise the \ion{Fe}{9} λ171.073 emission of a coronal loop supporting a standing kink MHD mode. The kink MHD wave solution of a plasma cylinder is mapped into a semi-torus structure to simulate a curved coronal loop. We decompose the solution into a quasi-rigid kink motion and a quadrupole term, which dominate the plasma inside and outside the flux tube, respectively. At the loop edges, the line-of-sight integrates relatively more ambient plasma, and the background emission becomes significant. The plasma motion associated with the ... [READ MORE]

Authors: Ding Yuan, Tom Van Doorsselaere
Projects: Hinode/EIS

Publication Status: ApJS in press
Last Modified: 2016-03-08 12:17
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Solar Coronal Jets: Observations, Theory, and Modeling  

Nour E. Raouafi   Submitted: 2016-07-06 15:34

Coronal jets represent important manifestations of ubiquitous solar transients, which may be the source of significant mass and energy input to the upper solar atmosphere and the solar wind. While the energy involved in a jet-like event is smaller than that of ?nominal? solar flares and coronal mass ejections (CMEs), jets share many common properties with these phenomena, in particular, the explosive magnetically driven dynamics. Studies of jets could, therefore, provide critical insight for understanding the larger, more complex drivers of the solar activity. On the other side of the size-spectrum, the study of jets could also supply important clues on the physics of transients close or at the limit of the current spatial resolution such as spicules. Furthermore, jet phenomena may hint ... [READ MORE]

Authors: N.E. Raouafi, S. Patsourakos, E. Pariat, P.R. Young, A.C. Sterling, A. Savcheva, M. Shimojo, F. Moreno-Insertis, C.R. DeVore, V. Archontis, T. T?r?k, H. Mason, W. Curdt, K. Meyer, K. Dalmasse, Y. Matsui
Projects: GOES X-rays ,Hinode/EIS,Hinode/SOT,Hinode/XRT,IRIS,Nobeyama Radioheliograph,RHESSI,SDO-AIA,SDO-HMI,SoHO-EIT,SoHO-MDI,SoHO-CDS,SoHO-LASCO,SoHO-SUMER,STEREO,TRACE,Yohkoh-HXT,Yohkoh-SXT

Publication Status: Published in Space Science Reviews. doi: 10.1007/s11214-016-0260-5
Last Modified: 2016-07-07 09:18
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Subject will be restored when possible  

Kathy Reeves   Submitted: 2008-04-15 16:04

We examine phenomena associated with eruptions in the two different regimes of the solar corona and the terrestrial magnetosphere. We find striking similarities between the speeds of shrinking magnetic field lines in the corona and dipolarization fronts traversing the magnetosphere. We also examine the similarities between supra-arcade downflows observed during solar flares and bursty bulk flows seen in the magnetotail, and find that these phenomena have remarkably similar speeds, velocity profiles and size scales. Thus we show manifest similarities in the magnetic reconfiguration in response to the ejection of coronal mass ejections in the corona and the ejection of plasmoids in the magnetotail. The subsequent return of loops to a quasi-potential state in the corona and field ... [READ MORE]

Authors: K. K. Reeves, T. B. Guild, W. J. Hughes, K. E. Korreck, J. Lin, J. Raymond, S. Savage, N. A. Schwadron, H. E. Spence, D. F. Webb, M. Wiltberger
Projects: Hinode/XRT,TRACE

Publication Status: in press
Last Modified: 2008-04-16 05:32
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Subject will be restored when possible  

Kathy Reeves   Submitted: 2008-04-15 16:04

We examine phenomena associated with eruptions in the two different regimes of the solar corona and the terrestrial magnetosphere. We find striking similarities between the speeds of shrinking magnetic field lines in the corona and dipolarization fronts traversing the magnetosphere. We also examine the similarities between supra-arcade downflows observed during solar flares and bursty bulk flows seen in the magnetotail, and find that these phenomena have remarkably similar speeds, velocity profiles and size scales. Thus we show manifest similarities in the magnetic reconfiguration in response to the ejection of coronal mass ejections in the corona and the ejection of plasmoids in the magnetotail. The subsequent return of loops to a quasi-potential state in the corona and field ... [READ MORE]

Authors: K. K. Reeves, T. B. Guild, W. J. Hughes, K. E. Korreck, J. Lin, J. Raymond, S. Savage, N. A. Schwadron, H. E. Spence, D. F. Webb, M. Wiltberger
Projects: Hinode/XRT,TRACE

Publication Status: in press
Last Modified: 2008-09-23 21:10
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The Relationship Between Solar Radio and Hard X-ray Emission  

Amir Caspi   Submitted: 2011-10-28 12:20

This review discusses the complementary relationship between radio and hard X-ray observations of the Sun using primarily results from the era of the Reuven Ramaty High Energy Solar Spectroscopic Imager satellite. A primary focus of joint radio and hard X-ray studies of solar flares uses observations of nonthermal gyrosynchrotron emission at radio wavelengths and bremsstrahlung hard X-rays to study the properties of electrons accelerated in the main flare site, since it is well established that these two emissions show very similar temporal behavior. A quantitative prescription is given for comparing the electron energy distributions derived separately from the two wavelength ranges: this is an important application with the potential for measuring the magnetic field strength in the ... [READ MORE]

Authors: Stephen M. White, Arnold O. Benz, Steven Christe, Frantisek Farnik, Mukul R. Kundu, Gottfried Mann, Zongjun Ning, Jean-Pierre Raulin, Adriana V. R. Silva-Valio, Pascal Saint-Hilaire, Nicole Vilmer, Alexander Warmuth
Projects: GONG,Hinode/EIS,Hinode/SOT,Hinode/XRT,Nobeyama Radioheliograph,Owens Valley Solar Array,RHESSI,SDO-AIA,SDO-HMI,SDO-EVE,SoHO-EIT,SoHO-MDI,SoHO-CDS,SoHO-LASCO,SoHO-SUMER,STEREO,TRACE

Publication Status: Published -- White, S. M., et al. 2011, Space Sci. Rev., 159, 225; DOI 10.1007/s11214-010-9708-1
Last Modified: 2011-11-17 14:19
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Global oscillations in a magnetic solar model II. - Oblique propagation  

Balazs Pinter   Submitted: 2007-02-01 02:24

The coupling of solar global acoustic oscillations to a magnetised solar atmosphere is studied here. The solar interior - atmosphere interface is modelled by a non-magnetic polytrope interior overlayed by a planar atmosphere embedded in non-uniform horizontal atmospheric magnetic field. Pinter and Goossens (1999,A&A,347,321) showed that parallel propagating acoustic waves can couple resonantly to local magnetohydrodynamic (MHD) slow continuum modes only. In general, global acoustic modes can, however, propagate in arbitrary directions with respect to local atmospheric fields giving rise to an additional efficient coupling mechanism that has consequences on mode damping and atmospheric energetics. In this paper we study obliquely propagating global modes that can couple also to local MHD ... [READ MORE]

Authors: Pint?r, B., Erd?lyi, R., Goossens, M.
Projects: Hinode

Publication Status: A&A (submitted)
Last Modified: 2007-02-01 09:29
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High-Energy Aspects of Solar Flares: Overview of the Volume  

Amir Caspi   Submitted: 2011-10-28 12:13

In this introductory chapter, we provide a brief summary of the successes and remaining challenges in understanding the solar flare phenomenon and its attendant implications for particle acceleration mechanisms in astrophysical plasmas. We also provide a brief overview of the contents of the other chapters in this volume, with particular reference to the well-observed flare of 2002 July 23

Authors: Brian R. Dennis, A. Gordon Emslie, Hugh S. Hudson
Projects: GONG,Hinode/EIS,Hinode/SOT,Hinode/XRT,Nobeyama Radioheliograph,Owens Valley Solar Array,RHESSI,SDO-AIA,SDO-HMI,SDO-EVE,SoHO-EIT,SoHO-MDI,SoHO-CDS,SoHO-LASCO,SoHO-SUMER,STEREO,TRACE

Publication Status: Published -- Dennis, B. R., et al. 2011, Space Sci. Rev., 159, 3; DOI 10.1007/s11214-011-9802-z
Last Modified: 2011-11-17 14:17
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Particle Acceleration by a Solar Flare Termination Shock  

Bin Chen   Submitted: 2015-12-08 18:53

Solar flares - the most powerful explosions in the solar system - are also efficient particle accelerators, capable of energizing a large number of charged particles to relativistic speeds. A termination shock is often invoked in the standard model of solar flares as a possible driver for particle acceleration, yet its existence and role have remained controversial. We present observations of a solar flare termination shock and trace its morphology and dynamics using high-cadence radio imaging spectroscopy. We show that a disruption of the shock coincides with an abrupt reduction of the energetic electron population. The observed properties of the shock are well-reproduced by simulations. These results strongly suggest that a termination shock is responsible, at least in part, for ... [READ MORE]

Authors: Bin Chen, Timothy S. Bastian, Chengcai Shen, Dale E. Gary, Sam Krucker, Lindsay Glesener
Projects: GOES X-rays ,Hinode/XRT,RHESSI,SDO-AIA,SoHO-LASCO,Very Large Array

Publication Status: Published on Science on December 4, 2015. 28 pages, 10 figures.
Last Modified: 2015-12-09 12:21
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Non-neutralized Electric Current Patterns in Solar Active Regions: Origin of the Shear-Generating Lorentz Force  

Manolis K. Georgoulis   Submitted: 2012-10-11 00:53

Using solar vector magnetograms of the highest available spatial resolution and signal-to-noise ratio we perform a detailed study of electric current patterns in two solar active regions: a flaring/eruptive, and a flare-quiet one. We aim to determine whether active regions inject non-neutralized (net) electric currents in the solar atmosphere, responding to a debate initiated nearly two decades ago that remains inconclusive. We find that well-formed, intense magnetic polarity inversion lines (PILs) within active regions are the only photospheric magnetic structures that support significant net current. More intense PILs seem to imply stronger non-neutralized current patterns per polarity. This finding revises previous works that claim frequent injections of intense non-neutralized ... [READ MORE]

Authors: M. K. Georgoulis, V. S. Titov, & Z. Mikic
Projects: Hinode/SOT

Publication Status: ApJ, in press
Last Modified: 2012-10-11 08:04
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Non-force-free extrapolation of solar coronal magnetic field using vector magnetograms  

qiang hu   Submitted: 2009-05-07 12:59

We report our recent improvement in non-force-free extrapolation of coronal magnetic field, using vector magnetograms. Based on the principle of minimum (energy) dissipation rate (MDR), a generally non-force-free magnetic field solution is expressed as the superposition of one potential field and two (constant-$alpha$) linear force-free fields, with distinct $alpha$ parameters. With a known potential field, the system is reduced to a second-order one that can be solved using one single-layer vector magnetogram. We devise an iteration procedure to determine the potential field, by achieving satisfactory agreement between the MDR-model computed and measured transverse magnetic field vectors on the bottom boundary. We illustrate this approach by applying it to real magnetograph ... [READ MORE]

Authors: Qiang Hu, B. Dasgupta, M. DeRosa, J. Buechner, G.A. Gary
Projects: Hinode/SOT

Publication Status: submitted
Last Modified: 2009-05-07 13:31
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Forecasting a CME by Spectroscopic Precursor?  

Deb Baker   Submitted: 2011-11-21 03:42

This abstract was corrupted following database problems and is being recovered. It will be restored as quickly as possible. Any questions, please send them to Alisdair. Sorry for any incovenience.


Authors: D. Baker, L. van Driel-Gesztelyi, L.M. Green
Projects: Hinode/EIS

Publication Status: Accepted for publication by Solar Physics
Last Modified: 2011-11-22 02:49
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Relaxation of magnetic field relative to plasma density revealed from microwave zebra patterns associated with solar flares  

Yihua Yan   Submitted: 2012-11-01 19:52

It is generally considered that the emission of microwave zebra pattern (ZP) structures requires high density and high temperatures, which is similar to the situation of the flaring region where primary energy releases. Therefore, the parameters analysis of ZPs may reveal the physical conditions of the flaring source region. This work investigates the variations of 74 microwave ZP structures observed by Chinese Solar Broadband Radio Spectrometer (SBRS/Huairou) at 2.6-3.8 GHz in 9 solar flares, and found that the ratio between the plasma density scale height LN and the magnetic field scale height LB in emission source displays a tendency of decrease during the flaring processes. The ratio LN/LB is about 3-5 before the maximum of flares. It decreases to about 2 after the maximum. The ... [READ MORE]

Authors: Sijie Yu, Yihua Yan, and Baolin Tan
Projects: ACE,GOES X-rays ,Hinode/XRT,Nobeyama Radioheliograph,TRACE

Publication Status: ApJ, accepted
Last Modified: 2012-11-04 15:13
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Title: Monte Carlo Markov Chain DEM reconstruction of isothermal plasmas  

Fabio Reale   Submitted: 2011-12-14 03:36

In this paper, we carry out tests on the Monte Carlo Markov Chain (MCMC) technique with the aim of determining: 1) its ability to retrieve isothermal plasmas from a set of spectral line intensities, with and without random noise; 2) to what extent can it discriminate between an isothermal solution and a narrow multithermal distribution; and 3) how well it can detect multiple isothermal components along the line of sight. We also test the effects of 4) atomic data uncertainties on the results, and 5) the number of ions whose lines are available for the DEM reconstruction. We find that the MCMC technique is unable to retrieve isothermal plasmas to better than Delta log T = 0.05. Also, the DEM curves obtained using lines calculated with an isothermal plasma and with a Gaussian distribution ... [READ MORE]

Authors: E. Landi, F. Reale, P. Testa
Projects: Hinode/EIS,Hinode/XRT,SDO-AIA,SDO-EVE,SoHO-CDS,SoHO-SUMER

Publication Status: accepted for publication in A&A
Last Modified: 2011-12-14 08:53
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Spatially-Resolved Nonthermal Line Broadening During the Impulsive Phase of a Solar Flare  

Ryan Milligan   Submitted: 2011-07-21 10:56

This abstract was corrupted following database problems and is being recovered. It will be restored as quickly as possible. Any questions, please send them to Alisdair. Sorry for any incovenience.


Authors: Ryan O. Milligan
Projects: Hinode/EIS

Publication Status: Accepted to The Astrophysics Journal
Last Modified: 2012-01-24 13:32
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Nonlinear force-free modelling: influence of inaccuracies in the measured magnetic vector  

Thomas Wiegelmann   Submitted: 2009-12-15 04:45

Context: Solar magnetic fields are regularly extrapolated into the corona starting from photospheric magnetic measurements that can suffer from significant uncertainties. Aims: Here we study how inaccuracies introduced into the maps of the photospheric magnetic vector from the inversion of ideal and noisy Stokes parameters influence the extrapolation of nonlinear force-free magnetic fields. Methods: We compute nonlinear force-free magnetic fields based on simulated vector magnetograms, which have been produced by the inversion of Stokes profiles, computed froma 3-D radiation MHD simulation snapshot. These extrapolations are compared with extrapolations starting directly from the field in the MHD simulations, which is our reference. We investigate how line formation and ... [READ MORE]

Authors: T. Wiegelmann, L. Yelles Chaouche, S. K. Solanki, A. Lagg
Projects: Hinode/SOT

Publication Status: Astronomy and Astrophysics, accepted,
Last Modified: 2009-12-15 12:20
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X-raying hot plasma in solar active regions with the SphinX spectrometer  

Fabio Reale   Submitted: 2012-07-26 04:49

The detection of very hot plasma in the quiescent corona is important for diagnosing heating mechanisms. The presence and the amount of such hot plasma is currently debated. The SphinX instrument on-board CORONAS-PHOTON mission is sensitive to X-ray emission well above 1 keV and provides the opportunity to detect the hot plasma component. We analyzed the X-ray spectra of the solar corona collected by the SphinX spectrometer in May 2009 (when two active regions were present). We modelled the spectrum extracted from the whole Sun over a time window of 17 days in the 1.34-7 keV energy band by adopting the latest release of the APED database. The SphinX broadband spectrum cannot be modelled by a single isothermal component of optically thin plasma and two components are necessary. In ... [READ MORE]

Authors: M. Miceli, F. Reale, S. Gburek, S. Terzo, M. Barbera, A. Collura, J. Sylwester, M. Kowalinski, P. Podgorski, M. Gryciuk
Projects: Hinode/XRT

Publication Status: accepted for publication in A&A
Last Modified: 2012-07-26 13:05
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Recent Advances in Understanding Particle Acceleration Processes in Solar Flares  

Amir Caspi   Submitted: 2011-10-28 12:22

We review basic theoretical concepts in particle acceleration, with particular emphasis on processes likely to occur in regions of magnetic reconnection. Several new developments are discussed, including detailed studies of reconnection in three-dimensional magnetic field configurations (e.g., current sheets, collapsing traps, separatrix regions) and stochastic acceleration in a turbulent environment. Fluid, test-particle, and particle-in-cell approaches are used and results compared. While these studies show considerable promise in accounting for the various observational manifestations of solar flares, they are limited by a number of factors, mostly relating to available computational power. Not the least of these issues is the need to explicitly incorporate the electrodynamic ... [READ MORE]

Authors: Valentina V. Zharkova, Karpar Arzner, Arnold O. Benz, Philippa Browning, Cyril Dauphin, A. Gordon Emslie, Lyndsay Fletcher, Eduard P. Kontar, Gottfried Mann, Marco Onofri, Vahe Petrosian, Rim Turkmani, Nicole Vilmer, Loukas Vlahos
Projects: GONG,Hinode/EIS,Hinode/SOT,Hinode/XRT,Nobeyama Radioheliograph,Owens Valley Solar Array,RHESSI,SDO-AIA,SDO-HMI,SDO-EVE,SoHO-EIT,SoHO-MDI,SoHO-CDS,SoHO-LASCO,SoHO-SUMER,STEREO,TRACE

Publication Status: Published -- Zharkova, V. V., et al. 2011, Space Sci. Rev., 159, 357; DOI 10.1007/s11214-011-9803-y
Last Modified: 2011-11-17 14:20
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Quasi-Periodic Pulsations in Solar Flares  

Victor Melnikov   Submitted: 2009-07-26 06:48

Quasi-periodic pulsations (QPP) are a common feature of flaring energy releases in the solar atmosphere, observed in all bands, from radio to hard X-ray. In this review we concentrate on QPP with the periods longer than one second. Physical mechanisms responsible for the generation of long QPP split into two groups: ?load/unload? mechanisms and MHD oscillations. Load/unload mechanisms are repetitive regimes of flaring energy releases by magnetic reconnection or by other means. MHD oscillations can affect all elements of the flaring emission generation: triggering of reconnection and modulation of its rate, acceleration and dynamics of non-thermal electrons, and physical conditions in the emitting plasmas. In the case of MHD oscillations, the periodicity of QPP is determined either by the ... [READ MORE]

Authors: Nakariakov, V. M. and Melnikov, V. F.
Projects: CORONAS-F/SPIRIT,Hinode/XRT,RHESSI,SoHO-MDI,SoHO-SUMER,TRACE,Yohkoh-HXT

Publication Status: Space Science Reviews (accepted), Online First
Last Modified: 2009-07-27 10:48
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Force-free field modeling of twist and braiding-induced magnetic energy in an active-region corona  

Julia K. Thalmann   Submitted: 2013-11-15 04:45

The theoretical concept that braided magnetic field lines in the solar corona may dissipate a sufficient amount of energy to account for the brightening observed in the active-region corona, has been substantiated by high-resolution observations only recently. From the analysis of coronal images obtained with the High Resolution Coronal Imager, first observational evidence of the braiding of magnetic field lines was reported by Cirtain et al. 2013 (hereafter CG13). We present nonlinear force-free reconstructions of the associated coronal magnetic field based on vector SDO/HMI magnetograms. We deliver estimates of the free magnetic energy associated to a braided coronal structure. Our model results suggest (~100 times) more free energy at the braiding site than analytically estimated by ... [READ MORE]

Authors: Thalmann, J. K., Tiwari, S. K., Wiegelmann, T.
Projects: Hinode/SOT,SDO-HMI

Publication Status: Accepted for publication in ApJ
Last Modified: 2013-11-17 13:30
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Subject will be restored when possible  

Katharine Reeves   Submitted: 2007-08-28 06:41

In this paper, we present numerical simulations of solar flares that couple a loss-of-equilibrium solar eruption model with a one-dimensional hydrodynamic model. In these calculations, the eruption is initiated by footpoint motions that disrupt the balance of forces acting on a flux rope. After the eruption begins, a current sheet forms and an arcade of flare loops is created by reconnecting magnetic fields. Thermal energy input into the flare loops is found by assuming the complete thermalization of the Poynting flux swept into the current sheet. This thermal energy is input into a 1D hydrodynamic code for each loop formed in the multi-threaded flare arcade. We find that a density enhancement occurs at the loop top when the two evaporating plasma fronts in each leg of the loop ... [READ MORE]

Authors: Reeves, K. K., Warren, H. P. and Forbes, T. G.
Projects: Hinode,TRACE,Yohkoh-BCS,Yohkoh-SXT

Publication Status: ApJ (in press)
Last Modified: 2007-08-28 06:41
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Scientific considerations for future spectroscopic measurements from space of activity on the Sun  

Gordon Holman   Submitted: 2016-12-23 11:11

High-resolution UV and X-ray spectroscopy are important to understanding the origin and evolution of magnetic energy release in the solar atmosphere, as well as the subsequent evolution of heated plasma and accelerated particles. Electromagnetic radiation is observed from plasma heated to temperatures ranging from about 10 kK to above 10 MK, from accelerated electrons emitting photons primarily at X-ray energies, and from ions emitting in γ rays. These observations require space-based instruments sensitive to emissions at wavelengths shorter than the near UV. This article reviews some recent observations with emphasis on solar eruptive events, the models that describe them, and the measurements they indicate are needed for substantial progress in the future. Specific examples are ... [READ MORE]

Authors: Gordon D. Holman
Projects: GOES X-rays,Hinode/EIS,IRIS,Other,RHESSI,SDO-AIA

Publication Status: Published in the Journal of Geophysical Research: Space Physics, 15 Dec 2016
Last Modified: 2016-12-28 11:41
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Magnetohydrodynamic Modeling of the Solar Eruption on 2010 April 8  

Bernhard Kliem   Submitted: 2014-07-11 09:00

The structure of the coronal magnetic field prior to eruptive processes and the conditions for the onset of eruption are important issues that can be addressed through studying the magnetohydrodynamic stability and evolution of nonlinear force-free field (NLFFF) models. This paper uses data-constrained NLFFF models of a solar active region that erupted on 2010 April 8 as initial condition in MHD simulations. These models, constructed with the techniques of flux rope insertion and magnetofrictional relaxation, include a stable, an approximately marginally stable, and an unstable configuration. The simulations confirm previous related results of magnetofrictional relaxation runs, in particular that stable flux rope equilibria represent key features of the observed pre-eruption coronal ... [READ MORE]

Authors: B. Kliem, Y. N. Su, A. A. van Ballegooijen, & E. E. DeLuca
Projects: Hinode/XRT,SDO-AIA,SDO-HMI,STEREO

Publication Status: Published in ApJ 779, 129, 2013
Last Modified: 2014-07-11 14:34
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Evidence of Impulsive Heating in Active Region Core Loops  

Durgesh Tripathi   Submitted: 2010-09-03 10:07

Using a full spectral scan of an active region from the Extreme-Ultraviolet Imaging Spectrometer (EIS) we have obtained Emission Measure EM(T) distributions in two different moss regions within the same active region. We have compared these with theoretical transition region EMs derived for three limiting cases, namely static equilibrium, strong condensation and strong evaporation from Klimchuk et al. (2008). The EM distributions in both the moss regions are strik- ingly similar and show a monotonically increasing trend from log T [K] = 5.15?6.3. Using photospheric abundances we obtain a consistent EM distribution for all ions. Comparing the observed and theoretical EM distributions, we find that the observed EM distribution is best explained by the strong condensation case (EMcon), ... [READ MORE]

Authors: Durgesh Tripathi, Helen E. Mason, James A. Klimchuk
Projects: Hinode/EIS

Publication Status: Accepted for publication in ApJ
Last Modified: 2010-09-03 20:23
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Can coronal hole spicules reach coronal temperatures?  

Maria Madjarska   Submitted: 2011-05-06 09:51

This abstract was corrupted following database problems and is being recovered. It will be restored as quickly as possible. Any questions, please send them to Alisdair. Sorry for any incovenience.


Authors: M.S. Madjarska, K. Vanninathan and J.G. Doyle
Projects: Hinode/EIS,Hinode/SOT,SoHO-SUMER

Publication Status: accepted in A&A
Last Modified: 2011-05-06 17:07
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Rapid Changes of Photospheric Magnetic Field After Tether-cutting Reconnection and Magnetic Implosion  

Chang Liu   Submitted: 2011-12-13 14:20

This abstract was corrupted following database problems and is being recovered. It will be restored as quickly as possible. Any questions, please send them to Alisdair. Sorry for any incovenience.


Authors: Chang Liu, Na Deng, Rui Liu, Jeongwoo Lee, Thomas Wiegelmann, Ju Jing, Yan Xu, Shuo Wang, and Haimin Wang
Projects: Hinode/SOT,RHESSI,SDO-AIA,SDO-HMI

Publication Status: ApJ Letters, accepted
Last Modified: 2011-12-13 14:37
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A Non-radial Eruption in a Quadrupolar Magnetic Configuration with a Coronal Null  

Xudong Sun   Submitted: 2012-08-06 18:14

We report one of several homologous non-radial eruptions from NOAA active region (AR) 11158 that are strongly modulated by the local magnetic field as observed with the Solar Dynamic Observatory (SDO). A small bipole emerged in the sunspot complex and subsequently created a quadrupolar flux system. Non-linear force-free field (NLFFF) extrapolation from vector magnetograms reveals its energetic nature: the fast-shearing bipole accumulated ~2e31 erg free energy (10% of AR total) over just one day despite its relatively small magnetic flux (5% of AR total). During the eruption, the ejected plasma followed a highly inclined trajectory, over 60 degrees with respect to the radial direction, forming a jet-like, inverted-Y shaped structure in its wake. Field extrapolation suggests complicated ... [READ MORE]

Authors: Xudong Sun, Todd Hoeksema, Yang Liu, Qingrong Chen, Keiji Hayashi
Projects: GOES X-rays ,Hinode/SOT,Hinode/XRT,RHESSI,SDO-AIA,SDO-HMI,STEREO

Publication Status: Accepted by ApJ
Last Modified: 2012-08-07 09:16
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Observing the release of twist by magnetic reconnection in a solar filament eruption  

Xiaoli Yan   Submitted: 2016-06-16 23:54

Magnetic reconnection is a fundamental process of topology change and energy release, taking place in plasmas on the Sun, in space, in astrophysical objects and in the laboratory. However, observational evidence has been relatively rare and typically only partial. Here we present evidence of fast reconnection in a solar filament eruption using high-resolution H-alpha images from the New Vacuum Solar Telescope, supplemented by extreme ultraviolet observations. The reconnection is seen to occur between a set of ambient chromospheric fibrils and the filament itself. This allows for the relaxation of magnetic tension in the filament by an untwisting motion, demonstrating a flux rope structure. The topology change and untwisting are also found through nonlinear force-free field modelling of ... [READ MORE]

Authors: Zhike Xue, Xiaoli Yan, Xin Cheng, Liheng Yang, Yingna Su, Bernhard Kliem, Jun Zhang, Zhong Liu, Yi Bi, Yongyuan Xiang, Kai Yang, Li Zhao
Projects: Hinode/XRT,New Vacuum Solar Telescope (NVST),SDO-AIA,SDO-HMI,SXI

Publication Status: Nature Communications, DOI:10.1038/NCOMMS11837
Last Modified: 2016-06-22 09:13
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On-disc Observations of Flux Rope Formation Prior to its Eruption  

Alexander James   Submitted: 2017-04-11 07:46

Coronal mass ejections (CMEs) are one of the primary manifestations of solar activity and can drive severe space weather effects. Therefore, it is vital to work towards being able to predict their occurrence. However, many aspects of CME formation and eruption remain unclear, including whether magnetic flux ropes are present before the onset of eruption and the key mechanisms that cause CMEs to occur. In this work, the pre-eruptive coronal configuration of an active region that produced an interplanetary CME with a clear magnetic flux rope structure at 1 AU is studied. A forward-S sigmoid appears in extreme-ultraviolet (EUV) data two hours before the onset of the eruption (SOL2012-06-14), which is interpreted as a signature of a right-handed flux rope that formed prior to the eruption. ... [READ MORE]

Authors: A. W. James, L. M. Green, E. Palmerio, G. Valori, H. A. S. Reid, D. Baker, D. H. Brooks, L. van Driel-Gesztelyi, E. K. J. Kilpua
Projects: GOES X-rays,Hinode/EIS,Nan?ay Radioheliograph,SDO-AIA,SDO-HMI

Publication Status: Accepted
Last Modified: 2017-04-11 23:28
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Statistical Study of Solar White-light Flares and Comparisons with Superflares on Solar-type Stars  

Kosuke Namekata   Submitted: 2017-11-04 04:30

Recently, many superflares on solar-type stars have been discovered as white-light flares (WLFs). The statistical study found a correlation between their energies ($E$) and durations ($\tau$): $\tau \propto E^{0.39}$ (Maehara et al. 2015, $EP\& S$, 67, 59), similar to those of solar hard/soft X-ray flares: $\tau \propto E^{0.2-0.33}$. This indicates a universal mechanism of energy release on solar and stellar flares, i.e., magnetic reconnection. We here carried out a statistical research on 50 solar WLFs observed with \textit{SDO}/HMI and examined the correlation between the energies and durations. As a result, the $E$--$\tau$ relation on solar WLFs ($\tau \propto E^{0.38}$) is quite similar to that on stellar superflares ($\tau \propto E^{0.39}$). However, the durations of ... [READ MORE]

Authors: Kosuke Namekata, Takahito Sakaue, Kyoko Watanabe, Ayumi Asai, Hiroyuki Maehara, Yuta Notsu, Shota Notsu, Satoshi Honda, Takako Ishii, Kai Ikuta, Daisaku Nogami, Kazunari Shibata
Projects: GOES X-rays,Hinode/SOT,RHESSI,SDO-AIA,SDO-HMI

Publication Status: accepted for publication in ApJ
Last Modified: 2017-11-06 11:34
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MHD modeling of coronal loops: injection of high-speed chromospheric flows  

Fabio Reale   Submitted: 2014-05-12 02:26

Observations reveal a correspondence between chromospheric type II spicules and bright upwardly moving fronts in the corona observed in the EUV band. However, theoretical considerations suggest that these flows are unlikely to be the main source of heating in coronal magnetic loops. We investigate the propagation of high-speed chromospheric flows into coronal magnetic flux tubes, and the possible production of emission in the EUV band. We simulate the propagation of a dense 10^4 K chromospheric jet upwards along a coronal loop, by means of a 2-D cylindrical MHD model, including gravity, radiative losses, thermal conduction and magnetic induction. The jet propagates in a complete atmosphere including the chromosphere and a tenuous cool (∼0.8 MK) corona, linked through a steep ... [READ MORE]

Authors: A. Petralia, F. Reale, S. Orlando, J. A. Klimchuk
Projects: Hinode/EIS,Hinode/SOT,SDO-AIA

Publication Status: accepted for publication in A&A
Last Modified: 2014-05-14 13:10
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Observations of flux rope formation prior to coronal mass ejections  

Bernhard Kliem   Submitted: 2014-07-11 08:55

Understanding the magnetic configuration of the source regions of coronal mass ejections (CMEs) is vital in order to determine the trigger and driver of these events. Observations of four CME productive active regions are presented here, which indicate that the pre-eruption magnetic configuration is that of a magnetic flux rope. The flux ropes are formed in the solar atmosphere by the process known as flux cancellation and are stable for several hours before the eruption. The observations also indicate that the magnetic structure that erupts is not the entire flux rope as initially formed, raising the question of whether the flux rope is able to undergo a partial eruption or whether it undergoes a transition in specific flux rope configuration shortly before the CME.

Authors: L. M. Green & B. Kliem
Projects: GOES X-rays ,Hinode/XRT,Yohkoh-SXT

Publication Status: Published in Proc. IAU Symp. 300, 209, 2013
Last Modified: 2014-07-11 14:34
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Warm and Fuzzy: Temperature and Density Analysis of an Fe XV EIS Loop  

Joan Schmelz   Submitted: 2011-07-11 09:40

This abstract was corrupted following database problems and is being recovered. It will be restored as quickly as possible. Any questions, please send them to Alisdair. Sorry for any incovenience.


Authors: J.T. Schmelz, L.A. Rightmire, S.H. Saar, J.A. Kimble, B.T. Worley, S. Pathak
Projects: Hinode/EIS

Publication Status: ApJ (in press)
Last Modified: 2011-07-11 10:02
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Energy and helicity budgets of solar quiet regions  

Kostas Tziotziou   Submitted: 2014-03-05 01:28

We investigate the free magnetic energy and relative magnetic helicity budgets of solar quiet regions. Using a novel non-linear force-free method requiring single solar vector magnetograms we calculate the instantaneous free magnetic energy and relative magnetic helicity budgets in 55 quiet-Sun vector magnetograms. As in a previous work on active regions, we construct here for the first time the (free) energy-(relative) helicity diagram of quiet-Sun regions. We find that quiet-Sun regions have no dominant sense of helicity and show monotonic correlations a) between free magnetic energy/relative helicity and magnetic network area and, consequently, b) between free magnetic energy and helicity. Free magnetic energy budgets of quiet-Sun regions represent a rather continuous extension of ... [READ MORE]

Authors: Tziotziou, K., Tsiropoula, G., Georgoulis, M.K., Kontogiannis, I.
Projects: Dutch Open Telescope,Hinode/SOT

Publication Status: A&A (in press)
Last Modified: 2014-03-05 12:25
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Subject will be restored when possible  

Katharine Reeves   Submitted: 2007-08-28 06:42

In this paper, we present numerical simulations of solar flares that couple a loss-of-equilibrium solar eruption model with a one-dimensional hydrodynamic model. In these calculations, the eruption is initiated by footpoint motions that disrupt the balance of forces acting on a flux rope. After the eruption begins, a current sheet forms and an arcade of flare loops is created by reconnecting magnetic fields. Thermal energy input into the flare loops is found by assuming the complete thermalization of the Poynting flux swept into the current sheet. This thermal energy is input into a 1D hydrodynamic code for each loop formed in the multi-threaded flare arcade. We find that a density enhancement occurs at the loop top when the two evaporating plasma fronts in each leg of the loop ... [READ MORE]

Authors: Reeves, K. K., Warren, H. P. and Forbes, T. G.
Projects: Hinode,TRACE,Yohkoh-BCS,Yohkoh-SXT

Publication Status: ApJ (in press)
Last Modified: 2007-08-30 21:35
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Determining the Intrinsic CME Flux Rope Type Using Remote-sensing Solar Disk Observations  

Erika Palmerio   Submitted: 2017-01-31 02:16

A key aim in space weather research is to be able to use remote-sensing observations of the solar atmosphere to extend the lead time of predicting the geoeffectiveness of a coronal mass ejection (CME). In order to achieve this, the magnetic structure of the CME as it leaves the Sun must be known. In this article we address this issue by developing a method to determine the intrinsic flux rope type of a CME solely from solar disk observations. We use several well known proxies for the magnetic helicity sign, the axis orientation, and the axial magnetic field direction to predict the magnetic structure of the interplanetary flux rope. We present two case studies: the 2 June 2011 and the 14 June 2012 CMEs. Both of these events erupted from an active region and, despite having clear in situ ... [READ MORE]

Authors: Palmerio, E., Kilpua, E. K. J., James, A. W., Green, L. M., Pomoell, J., Isavnin, A., and Valori, G.
Projects: GONG,Hinode/XRT,SDO-AIA,SDO-HMI,Wind

Publication Status: accepted for publication in Solar Physics
Last Modified: 2017-01-31 11:46
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The energetics of a global shock wave in the low solar corona  

David Long   Submitted: 2015-01-08 04:10

As the most energetic eruptions in the solar system, coronal mass ejections (CMEs) can produce shock waves at both their front and flanks as they erupt from the Sun into the heliosphere. However, the amount of energy produced in these eruptions, and the proportion of their energy required to produce the waves, is not well characterised. Here we use observations of a solar eruption from 2014 February 25 to estimate the energy budget of an erupting CME and the globally-propagating "EIT wave" produced by the rapid expansion of the CME flanks in the low solar corona. The "EIT wave" is shown using a combination of radio spectra and extreme ultraviolet images to be a shock front with a Mach number greater than one. Its initial energy is then calculated using the Sedov-Taylor blast-wave ... [READ MORE]

Authors: David M. Long, Deborah Baker, David R. Williams, Eoin P. Carley, Peter T. Gallagher, Pietro Zucca
Projects: Hinode/EIS,SDO-AIA

Publication Status: Accepted for publication in ApJ
Last Modified: 2015-01-09 12:50
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Spiky Fine Structure of Type III-like Radio Bursts in Absorption  

Gennady Chernov   Submitted: 2009-12-21 10:22

An uncommon fine structure in the radio spectrum consisting of bursts in absorption was observed with the Chinese Solar Broadband Radiospectrometer (SBRS) in the frequency range of 2.6 - 3.8 GHz during an X3.4/4B flare on 13 December 2006 in active region NOAA 10930 (S05W33). Usual fine structures in emission such as spikes, zebra stripes, and drifting fibers were observed at the peak of every new flare brightening. Within an hour at the decay phase of the event, we observed bursts consisting of spikes in absorption which pulsated periodically in frequency. Their instantaneous frequency bandwidths were found to be in the 75 MHz range. Moreover, in the strongest type III-like bursts in absorption, spikes showed stripes of the zebra-pattern (ZP), which drifted to higher frequencies. All ... [READ MORE]

Authors: G.P. Chernov, Y.H. Yan, C.M. Tan, B. Chen, Q.J. Fu
Projects: Hinode/XRT,TRACE

Publication Status: Accepted in Solar Physics
Last Modified: 2009-12-21 12:27
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Response to "Comment on 'Resolving the 180° Ambiguity in Solar Vector Magnetic Field Data: Evaluating the Effects of Noise, Spatial Resolution, and Method Assumptions' "  

K.D. Leka   Submitted: 2011-10-18 21:33

This abstract was corrupted following database problems and is being recovered. It will be restored as quickly as possible. Any questions, please send them to Alisdair. Sorry for any incovenience.


Authors: K.D. Leka, Graham Barnes, G. Allen Gary, A. D. Crouch, Y. Liu
Projects: Hinode/SOT

Publication Status: Accepted for Publication in Solar Physics. doi:10.1007/s11207-011-9879-2
Last Modified: 2011-10-19 09:21
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Microflares and the Statistics of X-ray Flares  

Amir Caspi   Submitted: 2011-10-28 12:21

This review surveys the statistics of solar X-ray flares, emphasising the new views that RHESSI has given us of the weaker events (the microflares). The new data reveal that these microflares strongly resemble more energetic events in most respects; they occur solely within active regions and exhibit high-temperature/nonthermal emissions in approximately the same proportion as major events. We discuss the distributions of flare parameters (e.g., peak flux) and how these parameters correlate, for instance via the Neupert effect. We also highlight the systematic biases involved in intercomparing data representing many decades of event magnitude. The intermittency of the flare/microflare occurrence, both in space and in time, argues that these discrete events do not explain general coronal ... [READ MORE]

Authors: I. G. Hannah, H. S. Hudson, M. Battaglia, S. Christe, J. Kasparova, S. Krucker, M. R. Kundu, A. Veronig
Projects: GONG,Hinode/EIS,Hinode/SOT,Hinode/XRT,Nobeyama Radioheliograph,Owens Valley Solar Array,RHESSI,SDO-AIA,SDO-HMI,SDO-EVE,SoHO-EIT,SoHO-MDI,SoHO-CDS,SoHO-LASCO,SoHO-SUMER,STEREO,TRACE

Publication Status: Published -- Hannah, I. G., et al. 2011, Space Sci. Rev., 159, 263; DOI 10.1007/s11214-010-9705-4
Last Modified: 2011-11-17 14:20
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Energy Release and Particle Acceleration in Flares: Summary and Future Prospects  

Amir Caspi   Submitted: 2011-10-28 12:23

RHESSI measurements relevant to the fundamental processes of energy release and particle acceleration in flares are summarized. RHESSI's precise measurements of hard X-ray continuum spectra enable model-independent deconvolution to obtain the parent electron spectrum. Taking into account the effects of albedo, these show that the low energy cut-off to the electron power-law spectrum is typically below tens of keV, confirming that the accelerated electrons contain a large fraction of the energy released in flares. RHESSI has detected a high coronal hard X-ray source that is filled with accelerated electrons whose energy density is comparable to the magnetic-field energy density. This suggests an efficient conversion of energy, previously stored in the magnetic field, into the bulk ... [READ MORE]

Authors: R.P. Lin
Projects: GONG,Hinode/EIS,Hinode/SOT,Hinode/XRT,Nobeyama Radioheliograph,Owens Valley Solar Array,RHESSI,SDO-AIA,SDO-HMI,SDO-EVE,SoHO-EIT,SoHO-MDI,SoHO-CDS,SoHO-LASCO,SoHO-SUMER,STEREO,TRACE

Publication Status: Published -- Lin, R. P. 2011, Space Sci. Rev., 159, 421; DOI 10.1007/s11214-011-9801-0
Last Modified: 2011-11-17 14:21
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Turbulent kinetic energy in the energy balance of a solar flare  

Eduard Kontar   Submitted: 2017-04-01 08:49

The energy released in solar flares derives from a reconfiguration of magnetic fields to a lower energy state, and is manifested in several forms, including bulk kinetic energy of the coronal mass ejection, acceleration of electrons and ions, and enhanced thermal energy that is ultimately radiated away across the electromagnetic spectrum from optical to X-rays. Using an unprecedented set of coordinated observations, from a suite of instruments, we here report on a hitherto largely overlooked energy component -- the kinetic energy associated with small-scale turbulent mass motions. We show that the spatial location of, and timing of the peak in, turbulent kinetic energy together provide persuasive evidence that turbulent energy may play a key role in the transfer of energy in solar flares. ... [READ MORE]

Authors: Kontar, E. P.; Perez, J. E.; Harra, L. K.; Kuznetsov, A. A.; Emslie, A. G.; Jeffrey, N. L. S.; Bian, N. H.; Dennis, B. R.
Projects: None,Hinode/EIS,RHESSI,SDO-AIA,SDO-HMI

Publication Status: to be published in Physical Review Letters
Last Modified: 2017-04-02 19:06
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Nonlinear Force-Free Extrapolation of Emerging Flux with a Global Twist and Serpentine Fine Structures  

Pascal Demoulin   Submitted: 2011-09-16 07:25

This abstract was corrupted following database problems and is being recovered. It will be restored as quickly as possible. Any questions, please send them to Alisdair. Sorry for any incovenience.


Authors: G. Valori, L.M. Green, P. Demoulin, S. Vargas Dominguez, L. van Driel-Gesztelyi, A. Wallace, D. Baker, M. Fuhrmann
Projects: Hinode/EIS,Hinode/SOT,Hinode/XRT

Publication Status: Solar Physics (in press)
Last Modified: 2011-09-16 08:40
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Simulation of the Formation of a Solar Active Region  

Mark Cheung   Submitted: 2010-06-21 15:01

We present a radiative magnetohydrodynamics simulation of the formation of an Active Region on the solar surface. The simulation models the rise of a buoyant magnetic flux bundle from a depth of 7.5 Mm in the convection zone up into the solar photosphere. The rise of the magnetic plasma in the convection zone is accompanied by predominantly horizontal expansion. Such an expansion leads to a scaling relation between the plasma density and the magnetic field strength such that $B propto varrho^{1/2}$. The emergence of magnetic flux into the photosphere appears as a complex magnetic pattern, which results from the interaction of the rising magnetic field with the turbulent convective flows. Small-scale magnetic elements at the surface first appear, followed by their gradual coalescence into ... [READ MORE]

Authors: M. C. M. Cheung, M. Rempel, A. M. Title, M. Sch?ssler
Projects: Hinode/SOT

Publication Status: Accepted for publication in ApJ
Last Modified: 2010-06-22 15:20
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Properties of Energetic Ions in the Solar Atmosphere from γ-Ray and Neutron Observations  

Amir Caspi   Submitted: 2011-10-28 12:19

Gamma-rays and neutrons are the only sources of information on energetic ions present during solar flares and on properties of these ions when they interact in the solar atmosphere. The production of {gamma}-rays and neutrons results from convolution of the nuclear cross-sections with the ion distribution functions in the atmosphere. The observed {gamma}-ray and neutron fluxes thus provide useful diagnostics for the properties of energetic ions, yielding strong constraints on acceleration mechanisms as well as properties of the interaction sites. The problem of ion transport between the accelerating and interaction sites must also be addressed to infer as much information as possible on the properties of the primary ion accelerator. In the last couple of decades, both theoretical and ... [READ MORE]

Authors: Nicole Vilmer, Alec L. MacKinnon, Gordon J. Hurford
Projects: GONG,Hinode/EIS,Hinode/SOT,Hinode/XRT,Nobeyama Radioheliograph,Owens Valley Solar Array,RHESSI,SDO-AIA,SDO-HMI,SDO-EVE,SoHO-EIT,SoHO-MDI,SoHO-CDS,SoHO-LASCO,SoHO-SUMER,STEREO,TRACE

Publication Status: Published -- Vilmer, N., et al. 2011, Space Sci. Rev., 159, 167; DOI 10.1007/s11214-010-9728-x
Last Modified: 2011-11-17 14:19
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Photospheric flux cancellation and associated flux rope formation and eruption  

Bernhard Kliem   Submitted: 2010-11-05 08:52

Aims: We study an evolving bipolar active region that exhibits flux cancellation at the internal polarity inversion line, the formation of a soft X-ray sigmoid along the inversion line and a coronal mass ejection. The aim is to investigate the quantity of flux cancellation that is involved in flux rope formation in the time period leading up to the eruption. Methods: The active region is studied using its extreme ultraviolet and soft X-ray emissions as it evolves from a sheared arcade to flux rope configuration. The evolution of the photospheric magnetic field is described and used to estimate how much flux is reconnected into the flux rope. Results: About one third of the active region flux cancels at the internal polarity inversion line in the 2.5 days leading up to the eruption. In ... [READ MORE]

Authors: L. M. Green, B. Kliem, A. J. Wallace
Projects: Hinode/EIS,Hinode/XRT,SoHO-MDI,SoHO-LASCO

Publication Status: Astron. Astrophys., in press
Last Modified: 2010-11-08 07:34
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The role of radiative losses in the late evolution of pulse-heated coronal loops/strands  

Fabio Reale   Submitted: 2012-05-22 04:25

Radiative losses from optically thin plasma are an important ingredient for modeling plasma confined in the solar corona. Spectral models are continuously updated to include the emission from more spectral lines, with significant effects on radiative losses, especially around 1 MK. We investigate the effect of changing the radiative losses temperature dependence due to upgrading of spectral codes on predictions obtained from modeling plasma confined in the solar corona. The hydrodynamic simulation of a pulse-heated loop strand is revisited comparing results using an old and a recent radiative losses function. We find significant changes in the plasma evolution during the late phases of plasma cooling: when the recent radiative loss curve is used, the plasma cooling rate increases ... [READ MORE]

Authors: F. Reale, E. Landi
Projects: Hinode/EIS,Hinode/XRT,SDO-AIA,TRACE

Publication Status: accepted for publication in A&A
Last Modified: 2012-05-22 08:56
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Observation of High-speed Outflow on Plume-like Structures of the Quiet Sun and Coronal Holes with SDO/AIA  

Hui Tian   Submitted: 2011-05-17 14:55

This abstract was corrupted following database problems and is being recovered. It will be restored as quickly as possible. Any questions, please send them to Alisdair. Sorry for any incovenience.


Authors: Hui Tian, Scott W. McIntosh, Shadia Rifal Habbal, Jiansen He
Projects: Hinode/EIS,SDO-AIA,STEREO

Publication Status: ApJ, in press
Last Modified: 2011-05-17 19:26
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Subject will be restored when possible  

Teimuraz Zaqarashvili   Submitted: 2008-02-22 00:48

Observations show the increase of high-frequency wave power near magnetic network cores and active regions in the solar lower atmosphere. This phenomenon can be explained by the interaction of acoustic waves with a magnetic field. We consider small-scale, bipolar, magnetic field canopy structure near the network cores and active regions overlying field-free cylindrical cavities of the photosphere. Solving the plasma equations we get the analytical dispersion relation of acoustic oscillations in the field-free cavity area. We found that the m = 1 mode, where m is azimuthal wave number, cannot be trapped under the canopy due to energy leakage upwards. However, higher (m > 1) harmonics can be easily trapped leading to the observed acoustic power halos under the canopy.

Authors: D. Kuridze, T. V. Zaqarashvili, B. M. Shergelashvili1, S. Poedts
Projects: Hinode/SOT

Publication Status: Accepted in Annales Geophysicae
Last Modified: 2008-09-23 21:25
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The Magnetic Energy - Helicity Diagram of Solar Active Regions  

Kostas Tziotziou   Submitted: 2012-09-26 02:49

Using a recently proposed nonlinear force-free method designed for single vector magnetograms of solar active regions we calculate the instantaneous free magnetic energy and relative magnetic helicity budgets in 162 vector magnetograms corresponding to 42 different active regions. We find a statistically robust, monotonic correlation between the free magnetic energy and the relative magnetic helicity in the studied regions. This correlation implies that magnetic helicity, besides free magnetic energy, may be an essential ingredient for major solar eruptions. Eruptive active regions appear well segregated from non-eruptive ones in both free energy and relative helicity with major (at least M-class) flares occurring in active regions with free energy and relative helicity exceeding ... [READ MORE]

Authors: K.Tziotziou, M.K. Georgoulis & N-E. Raouafi
Projects: Hinode/SOT

Publication Status: ApJ Letters, in press
Last Modified: 2012-09-26 09:09
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Signatures of the non-Maxwellian kappa-distributions in optically thin line spectra I. Theory and synthetic Fe IX--XIII spectra  

Jaroslav Dudik   Submitted: 2014-09-23 08:40

We investigate the possibility of diagnosing the degree of departure from the Maxwellian distribution using single-ion spectra originating in astrophysical plasmas in collisional ionization equilibrium. New atomic data for excitation of Fe IX-XIII are integrated under the assumption of a kappa-distribution of electron energies. Diagnostic methods using lines of a single ion formed at any wavelength are explored. Such methods minimize uncertainties from the ionization and recombination rates, as well as the possible presence of non-equilibrium ionization. Approximations to the collision strengths are also investigated. The calculated intensities of most of the Fe IX-XIII EUV lines show consistent behaviour with kappa at constant temperature. Intensities of these lines decrease with kappa, ... [READ MORE]

Authors: Dudik, J, Del Zanna, G., Mason, H.E., Dzifcakova, E.
Projects: Hinode/EIS

Publication Status: to appear in Astronomy & Astrophysics
Last Modified: 2014-09-23 10:49
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Response of the Photospheric Magnetic Field to the X2.2 Flare on 2011 February 15  

Shuo Wang   Submitted: 2011-12-16 12:43

This abstract was corrupted following database problems and is being recovered. It will be restored as quickly as possible. Any questions, please send them to Alisdair. Sorry for any incovenience.


Authors: Shuo Wang, Chang Liu, Rui Liu, Na Deng, Yang Liu, and Haimin Wang
Projects: Hinode/SOT,RHESSI,SDO-AIA,SDO-HMI

Publication Status: ApJ Letters, accepted
Last Modified: 2011-12-19 09:06
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Coronal hole boundaries at small scales: IV. SOT view-Magnetic field properties of small-scale transient brightenings in coronal holes  

Zhenghua Huang   Submitted: 2012-10-05 15:41

We study the magnetic properties of small-scale transients in coronal holes and a few in the quiet Sun identified in X-ray observations in paper II and analysed in spectroscopic data in paper III. We aim to investigate the role of small-scale transients in the evolution of the magnetic field in an equatorial coronal hole. Two sets of observations of an equatorial coronal hole and another two in quiet-Sun regions were analysed using longitudinal magnetograms taken by the Solar Optical Telescope. An automatic feature tracking program, SWAMIS, was used to identify and track the magnetic features. Each event was then visually analysed in detail. In both coronal holes and quiet-Sun regions, all brightening events are associated with bipolar regions and caused by magnetic flux emergence ... [READ MORE]

Authors: Z. Huang, M. S. Madjarska, J. G. Doyle, D. A. Lamb
Projects: Hinode/SOT,Hinode/XRT

Publication Status: Accepted by A&A
Last Modified: 2012-10-10 09:03
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3D MHD modeling of twisted coronal loops  

Fabio Reale   Submitted: 2016-07-20 08:01

We perform MHD modeling of a single bright coronal loop to include the interaction with a non-uniform magnetic field. The field is stressed by random footpoint rotation in the central region and its energy is dissipated into heating by growing currents through anomalous magnetic diffusivity that switches on in the corona above a current density threshold. We model an entire single magnetic flux tube, in the solar atmosphere extending from the high-beta chromosphere to the low-beta corona through the steep transition region. The magnetic field expands from the chromosphere to the corona. The maximum resolution is ~30 km. We obtain an overall evolution typical of loop models and realistic loop emission in the EUV and X-ray bands. The plasma confined in the flux tube is heated to active ... [READ MORE]

Authors: F. Reale, S. Orlando, M. Guarrasi, A. Mignone, G. Peres, A. W. Hood, E. R. Priest
Projects: Hinode/XRT,SDO-AIA

Publication Status: accepted for publication in ApJ
Last Modified: 2016-07-20 12:23
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Relations between strong high-frequency microwave bursts and proton events  

Victor Grechnev   Submitted: 2013-08-13 01:23

Proceeding from close association between solar eruptions, flares, shock waves, and CMEs, we analyze relations between bursts at 35 GHz recorded with the Nobeyama Radio Polarimeters during 1990-2012, on the one hand, and solar energetic particle (SEP) events, on the other hand. Most west to moderately east solar events with strong bursts at 35 GHz produced near-Earth proton enhancements of J(E > 100 MeV) > 1 pfu. The strongest and hardest those caused ground level enhancements. There is a general, although scattered, correspondence between proton enhancements and peak fluxes at 35 GHz, especially pronounced if the 35 GHz flux exceeds 10^4 sfu and the microwave peak frequency is high. These properties indicate emission from numerous high-energy electrons in very strong magnetic fields ... [READ MORE]

Authors: V. Grechnev, N. Meshalkina, I. Chertok, V. Kiselev
Projects: GOES Particles,GOES X-rays ,Hinode/SOT,Neutron Monitors,Nobeyama Radioheliograph,Owens Valley Solar Array,SDO-AIA,SoHO-MDI,TRACE,Yohkoh-HXT

Publication Status: PASJ, accepted
Last Modified: 2013-08-13 11:02
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High-Cadence and High-Resolution Halpha Imaging Spectroscopy of a Circular Flare's Remote Ribbon with IBIS  

Na Deng   Submitted: 2013-04-16 07:46

We present an unprecedented high-resolution ha imaging spectroscopic observation of a C4.1 flare taken with the Interferometric Bidimensional Spectrometer (IBIS) in conjunction with the adaptive optics system at the 76~cm Dunn Solar Telescope on 2011 October 22 in active region NOAA 11324. Such a two-dimensional spectroscopic observation covering the entire evolution of a flare ribbon with high spatial (0.1arcpix image scale), cadence (4.8~s) and spectral (0.1~AA stepsize) resolution is rarely reported. The flare consists of a main circular ribbon that occurred in a parasitic magnetic configuration and a remote ribbon that was observed by the IBIS. Such a circular-ribbon flare with a remote brightening is predicted in 3D fan-spine reconnection but so far has been rarely ... [READ MORE]

Authors: Na Deng, Alexandra Tritschler, Ju Jing, Xin Chen, Chang Liu, Kevin Reardon, Carsten Denker, Yan Xu, and Haimin Wang
Projects: Hinode/SOT,National Solar Observatory (Sac Peak),RHESSI,SDO-AIA,SDO-HMI

Publication Status: The Astrophysical Journal, accepted
Last Modified: 2013-04-17 12:22
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Thermal Fronts in Flaring Magnetic Loops  

Victor Melnikov   Submitted: 2009-06-22 20:20

We examine the existence of thermal fronts in solar flaring magnetic loops. In the past, two opposite conclusions have been made from the analysis of the evolution of a system in which hot electrons are injected into a coronal magnetic loop. One, made on the basis of analytical solutions, claims that this leads to the formation of ion-acoustic turbulence and subsequently a thermal front develops, while the opposing view obtained later on the basis of detailed numerical modeling shows no evidence of thermal fronts. In our study a one dimensional Vlasov solver is implemented to solve the distribution functions for each particle species f_a(r, v, t ). The numerical simulations are electrostatic since we examine motions along the field lines only. The results presented here show that earlier ... [READ MORE]

Authors: Arber, T. D., Melnikov, V. F.
Projects: Hinode/XRT,RHESSI

Publication Status: ApJ 2009, V.690, P.238-243
Last Modified: 2009-06-23 07:30
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Magnetic Energy and Helicity Budgets in the Active-Region Solar Corona. II. Nonlinear Force-Free Approximation  

Manolis K. Georgoulis   Submitted: 2012-09-26 02:44

Expanding on an earlier work that relied on linear force-free magnetic fields, we self-consistently derive the instantaneous free magnetic energy and relative magnetic helicity budgets of an unknown three-dimensional nonlinear force-free magnetic structure extending above a single, known lower-boundary magnetic field vector. The proposed method does not rely on the detailed knowledge of the three-dimensional field configuration but is general enough to employ only a magnetic connectivity matrix on the lower boundary. The calculation yields a minimum free magnetic energy and a relative magnetic helicity consistent with this free magnetic energy. The method is directly applicable to photospheric or chromospheric vector magnetograms of solar active regions. Upon validation, it basically ... [READ MORE]

Authors: M. K. Georgoulis, K. Tziotziou, & N.-E. Raouafi
Projects: Hinode/SOT

Publication Status: ApJ, in press
Last Modified: 2012-09-26 09:10
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Phase relations for seismology of photospheric flux tubes  

Michael Ghislain Moreels   Submitted: 2013-03-07 00:54

We present a mathematical framework for the seismology of photospheric flux tubes using a uniform straight cylinder as a flux-tube model. In contrast to the earlier model of Fujimura & Tsuneta (2009), we also include a non-zero gas pressure; we do not use the thin tube approximation and we use an underdense region inside the flux tube. We used the linearised ideal magnetohydrodynamic equations to describe different wave modes in the photosphere. Using the wave mode polarisations we then obtained phase relations which represent different observables. Those phase relations were used to calculate phase differences and amplitude ratios. Finally we inverted these amplitude ratios to obtain plasma parameters which are not directly observable. The mathematical framework results in phase ... [READ MORE]

Authors: M. G. Moreels and T. Van Doorsselaere
Projects: Hinode/SOT

Publication Status: Accepted
Last Modified: 2013-03-07 06:54
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Spectroscopic analysis of interaction between an EIT wave and a coronal upflow region  

Feng Chen   Submitted: 2011-07-27 07:58

We report a spectroscopic analysis of an EIT wave event that occurred in active region 11081 on 2010 June 12 and was associated with an M2.0 class flare. The wave propagated near circularly. The south-eastern part of the wave front passed over an upflow region nearby a magnetic bipole. Using EIS raster observations for this region, we studied the properties of plasma dynamics in the wave front, as well as the interaction between the wave and the upflow region. We found a weak blueshift for the Fe XII {lambda}195.12 and Fe XIII {lambda}202.04 lines in the wave front. The local velocity along the solar surface, which is deduced from the line of sight velocity in the wave front and the projection effect, is much lower than the typical propagation speed of the wave. A more interesting ... [READ MORE]

Authors: F. Chen, M. D. Ding, P. F. Chen and L. K. Harra
Projects: Hinode/EIS

Publication Status: ApJ accepted for publication
Last Modified: 2011-07-29 00:43
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Resolving the 180◦ Ambiguity in Solar Vector Magnetic Field Data: Evaluating the Effects of Noise, Spatial Resolution, and Method Assumptions  

K D Leka   Submitted: 2009-08-11 18:08

The objective testing of algorithms for performing ambiguity resolution in vector magnetic field data is continued, with an examination of the effects of noise in the data. Through the use of analytic magnetic field models, two types of noise are ?added? prior to resolving: noise to simulate Poisson photon noise in the observed polarization spectra, and a spatial binning to simulate the effects of unresolved structure. The results are compared through the use of quantitative metrics and performance maps. We find that while no algorithm severely propagates the effects of Poisson noise beyond very local influences, some algorithms are more robust against high photon-noise levels than others. In the case of limited spatial resolution, loss of information regarding ... [READ MORE]

Authors: K.D. Leka ? Graham Barnes ? A.D. Crouch ? Thomas R. Metcalf ? G. Allen Gary ? Ju Jing ? Y. Liu
Projects: Hinode/SOT

Publication Status: Solar Physics (accepted)
Last Modified: 2009-08-12 07:25
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A nanoflare based cellular automaton model and the observed properties of the coronal plasma  

Marcelo Lopez-Fuentes   Submitted: 2016-08-04 12:21

We use the cellular automaton model described in L\'opez Fuentes \& Klimchuk (2015, ApJ, 799, 128) to study the evolution of coronal loop plasmas. The model, based on the idea of a critical misalignment angle in tangled magnetic fields, produces nanoflares of varying frequency with respect to the plasma cooling time. We compare the results of the model with active region (AR) observations obtained with the Hinode/XRT and SDO/AIA instruments. The comparison is based on the statistical properties of synthetic and observed loop lightcurves. Our results show that the model reproduces the main observational characteristics of the evolution of the plasma in AR coronal loops. The typical intensity fluctuations have an amplitude of 10 to 15\% both for the model and the observations. The sign of ... [READ MORE]

Authors: M. L?pez Fuentes, J.A. Klimchuk
Projects: None

Publication Status: Accepted for publication in ApJ
Last Modified: 2016-08-05 15:28
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Forward-Modeling of Doppler Shifts in EUV Spectral Lines  

Y Taroyan   Submitted: 2013-12-13 09:17

The interpretation of red- and blueshifts in EUV spectral observations remains a challenge that could provide important clues to the heating processes in the solar atmosphere. Hinode/EUV Imaging Spectrometer (EIS) observations near the footpoints of coronal loops show blueshifts for emission lines with temperatures above 1 MK and redshifts for lines below 1 MK. The implications are addressed through numerical modeling of loop dynamics. The simulation results are converted into synthetic EIS observations. A single one-dimensional loop cannot reproduce the observed behavior. However, persistent red- and blueshifts can be understood as a collective spectral signature of a bundle of 10 or more loops that have an average temperature of around 1 MK and evolve in a similar way: small-scale ... [READ MORE]

Authors: Y. Taroyan, S. J. Bradshaw
Projects: None

Publication Status: published
Last Modified: 2013-12-13 11:47
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What can we learn about solar coronal mass ejections, coronal dimmings, and Extreme-Ultraviolet jets through spectroscopic observations?  

Hui Tian   Submitted: 2012-01-10 16:02

Solar eruptions, particularly coronal mass ejections (CMEs) and extreme-ultraviolet (EUV) jets, have rarely been investigated with spectroscopic observations. We analyze several data sets obtained by the EUV Imaging Spectrometer onboard Hinode and find various types of flows during CMEs and jet eruptions. CME-induced dimming regions are found to be characterized by significant blueshift and enhanced line width by using a single Gaussian fit. While a red-blue (RB) asymmetry analysis and a RB-guided double Gaussian fit of the coronal line profiles indicate that these are likely caused by the superposition of a strong background emission component and a relatively weak (~10%) high-speed (~100 km s-1) upflow component. This finding suggests that the outflow velocity in the dimming ... [READ MORE]

Authors: Hui Tian, Scott W. McIntosh, Lidong Xia, Jiansen He, Xin Wang
Projects: None

Publication Status: ApJ, in press
Last Modified: 2012-01-11 09:11
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Subject will be restored when possible  

Pavol Schwartz   Submitted: 2008-09-18 05:27

A quiescent prominence was observed by several instruments on 2007 April 25. The temporal evolution was recorded in H_alpha by Hinode/SOT, in X-rays by Hinode/XRT and in the 195 A channel by TRACE. Moreover, ground-based observatories (GBO) provided calibrated H_alpha intensities. Simultaneous EUV data were also taken by the Hinode/EIS and SOHO/SUMER-CDS spectrometers. Here we have selected the SOT H_alpha image taken at 13:19 UT which nicely shows the prominence fine structure. We compare this image with co-temporal ones taken by XRT and TRACE and show the intensity variations along several cuts parallel to the solar limb. EIS spectra were obtained about half an hour later. Dark prominence structure clearly seen in the TRACE and EIS 195 A images is due to the prominence absorption in ... [READ MORE]

Authors: P. Heinzel, B. Schmieder, F. F?rn?k, P. Schwartz, N. Labrosse, P. Kotr?, U. Anzer, G. Molodij, A. Berlicki, E. E. DeLuca, L. Golub, T. Watanabe, and T. Berger
Projects: None

Publication Status: in press, accepted: 2008 June 9
Last Modified: 2008-09-18 05:27
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Observation of a Quasi-periodic Pulsation in Hard X-ray, Radio and Extreme-ultraviolet Wavelengths  

Pankaj Kumar   Submitted: 2016-03-14 20:13

We present multi-wavelength analysis of a quasi-periodic pulsation (QPP) observed in the hard X-ray, radio, and extreme-ultraviolet (EUV) channels during an M1.9 flare occurred on 23-24 September 2011. The non-thermal hard X-ray emission in 25-50 keV observed by RHESSI shows five distinct impulsive peaks of decaying amplitude with a period of about three minutes. Similar QPP was observed in the microwave emission recorded by the Nobeyama Radioheliograph and Polarimeter in the 8.8, 15, 17 GHz channels. Interestingly, the 3-min QPP was also observed in the metric and decimetric radio frequencies (25-180, 245, 610 MHz) as repetitive type III bursts. Multi-wavelength observations from the SDO/AIA, Hinode/SOT, and STEREO/SECCHI suggest a fan-spine topology at the eruption site, ... [READ MORE]

Authors: Pankaj Kumar, Valery M. Nakariakov, Kyung-Suk Cho
Projects: None

Publication Status: ApJ (in press)
Last Modified: 2016-03-15 11:24
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Interactive Multi-Instrument Database of Solar Flares  

Viacheslav Sadykov   Submitted: 2017-02-15 15:42

Solar flares represent a complicated physical phenomenon observed in a broad range of the electromagnetic spectrum, from radiowaves to gamma-rays. For a complete understanding of the flares it is necessary to perform a combined multi-wavelength analysis using observations from many satellites and ground-based observatories. For efficient data search, integration of different flare lists and representation of observational data, we have developed the Interactive Multi-Instrument Database of Solar Flares (\url{https://solarflare.njit.edu/}). The web database if fully functional and allows the user to search for uniquely-identified flare events based on their physical descriptors and availability of observations of a particular set of instruments. Currently the data from three primary flare ... [READ MORE]

Authors: Viacheslav M Sadykov, Rishabh Gupta, Alexander G Kosovichev, Vincent Oria, Gelu M Nita
Projects: Other

Publication Status: Submitted to Solar Physics journal
Last Modified: 2017-02-16 08:47
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Subject will be restored when possible  

Aveek Sarkar   Submitted: 2007-10-11 02:47

There is a growing body of evidence that the plasma loops seen with current instrumentation (SOHO, TRACE and Hinode) may consist of many subresolution elements or strands. Thus, the overall plasma evolution we observe in these features could be the cumulative result of numerous individual strands undergoing sporadic heating. This paper presents a short (109 cm ≡ 10 Mm) `global loop' as 125 individual strands where each strand is modelled independently by a one-dimensional hydrodynamic simulation. The energy release mechanism across the strands consists of localised, discrete heating events (nano-flares). The strands are `coupled' together through the frequency distribution of the total energy input to the loop which follows a power law distribution with index α. The location ... [READ MORE]

Authors: Aveek Sarkar, Robert W Walsh
Projects: None

Publication Status: ApJ(accepted)
Last Modified: 2008-04-22 16:28
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Study of Two Successive Three-Ribbon Solar Flares on 2012 July 6  

Haimin Wang   Submitted: 2013-12-23 19:02

This Letter reports two rarely observed three-ribbon flares (M1.9 and C9.2) on 2012 July 6 in NOAA AR 11515, which we found with Halpha observations of 0.1'' resolution from the New Solar Telescope and CaII H images from Hinode. The flaring site is characterized with an intriguing ''fish-bone-like'' morphology evidenced by both Halpha images and a nonlinear force-free field (NLFFF) extrapolation, where two semi-parallel rows of low-lying, sheared loops connect an elongated, parasitic negative field with the sandwiching positive fields. The NLFFF model also shows that the two rows of loops are asymmetric in height and have opposite twists, and are enveloped by large-scale field lines including open fields. The two flares occurred in succession in half an hour and are located at the two ... [READ MORE]

Authors: Haimin Wang, Chang Liu, Na Deng, Zhicheng Zeng, Yan Xu, Ju Jing and Wenda Cao
Projects: None

Publication Status: ApJL accepted
Last Modified: 2013-12-24 06:12
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Forward Modeling Transient Brightenings and Microflares around an Active Region Observed with Hi-C  

Adam Kobelski   Submitted: 2014-08-25 18:25

Small scale flare-like brightenings around active regions are among the smallest and most fundamental of energetic transient events in the corona, providing a testbed for models of heating and active region dynamics. In a previous study, we modeled a large collection of these microflares observed with Hinode/XRT using EBTEL and found that they required multiple heating events, but could not distinguish between multiple heating events on a single strand, or multiple strands each experiencing a single heating event. We present here a similar study, but with EUV data of Active Region 11520 from the High Resolution Coronal Imager (Hi-C) sounding rocket. Hi- C provides an order of magnitude improvement to the spatial resolution of XRT, and a cooler temperature sensitivity, which combine to ... [READ MORE]

Authors: Adam R. Kobelski, David E. McKenzie
Projects: Hi-C

Publication Status: ApJ (Accepted)
Last Modified: 2014-08-27 12:58
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Observational Study on the Fine Structure and Dynamics of a Solar Jet. I. Energy Build-Up Process around a Satellite Spot.  

Takahito Sakaue   Submitted: 2017-07-09 13:09

We report a solar jet phenomenon associated with successive flares on November 10th 2014. These explosive events were involved with the satellite spots' emergence around a delta-type sunspot in the decaying active region NOAA 12205. The data of this jet was provided by Solar Dynamic Observatory (SDO), X-Ray Telescope (XRT) aboard Hinode, Interface Region Imaging Spectrograph (IRIS) and Domeless Solar Telescope (DST) at Hida Observatory, Kyoto University. These plentiful data enabled us to present this series of papers to discuss the entire processes of the observed phenomena including the energy storage, event trigger, and energy release. In this paper, we focus on the energy build-up and trigger phases, by analyzing the photospheric horizontal flow field around the active region with an ... [READ MORE]

Authors: Takahito SAKAUE, Akiko TEI, Ayumi ASAI, Satoru UENO, Kiyoshi ICHIMOTO, Kazunari SHIBATA
Projects: None

Publication Status: accepted for publication in PASJ
Last Modified: 2017-07-11 11:22
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Modeling A Shallow Solar Dynamo  

kenneth schatten   Submitted: 2009-07-12 12:01

Abstract Photospheric ephemeral regions (EPRs) cover the Sun like a magnetic carpet. From this, we update the Babcock ? Leighton solar dynamo. Rather than sunspot fields appearing in the photosphere de novo from eruptions originating in the deep interior, we consider that sunspots form directly in the photosphere by a rapid accumulation of like-sign field from EPRs. This would only occur during special circumstances: locations and times when the temperature structure is highly superadiabatic and contains a large subsurface horizontal magnetic field (only present in the Sun?s lower latitudes). When these conditions are met, superadiabatic percolation occurs, wherein an inflow and downflow of gas scours the surface of EPRs to form active regions. When these conditions are not met, ... [READ MORE]

Authors: kenneth schatten
Projects: None

Publication Status: published in solar physics Solar Phys (2009) 255: 3?38
Last Modified: 2009-07-13 09:15
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Observation of kink instability during small B5.0 solar flare on 04 June, 2007  

Dr. A.K. Srivastava   Submitted: 2010-04-14 04:34

egin{abstract} Using multi-wavelength observations of SoHO/MDI, SOT-Hinode/blue-continuum (4504 AA), G-band (4305 AA), Ca II H (3968 AA) and TRACE 171 AA, we present the observational signature of highly twisted magnetic loop in AR 10960 during the period 04:43 UT-04:52 UT at 4 June, 2007. SOT-Hinode/blue-continuum (4504 AA) observations show that penumbral filaments of positive polarity sunspot have counter-clock wise twist, which may be caused by the clock-wise rotation of the spot umbrae. The coronal loop, whose one footpoint is anchored in this sunspot, shows strong right-handed twist in chromospheric SOT-Hinode/Ca II H (3968 AA) and coronal TRACE 171 AA, images. The length and the radius of the loop are $Lsim$80 Mm and $asim$4.0 Mm respectively. The distance between ... [READ MORE]

Authors: A.K. Srivastava; T.V. Zaqarashvili; Pankaj Kumar; M.L. Khodachenko
Projects: None

Publication Status: Accepted in The Astrophysical Journal
Last Modified: 2010-04-14 07:29
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Chromospheric evaporation in sympathetic coronal bright points  

Qingmin Zhang   Submitted: 2013-07-29 19:16

{Chromospheric evaporation is a key process in solar flares that has extensively been investigated using the spectroscopic observations. However, direct soft X-ray (SXR) imaging of the process is rare, especially in remote brightenings associated with the primary flares that have recently attracted dramatic attention.} {We intend to find the evidence for chromospheric evaporation and figure out the cause of the process in sympathetic coronal bright points (CBPs), i.e., remote brightenings induced by the primary CBP.} {We utilise the high-cadence and high-resolution SXR observations of CBPs from the X-ray Telescope (XRT) aboard the Hinode spacecraft on 2009 August 23.} {We discover thermal conduction front propagating from the primary ... [READ MORE]

Authors: Q. M. Zhang and H. S. Ji
Projects: None

Publication Status: accepted by A&A Letters
Last Modified: 2013-07-30 13:35
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Solar source of energetic particles in interplanetary space during the 2006 December 13 event  

Chuan Li   Submitted: 2009-07-17 05:20

An X3.4 solar are and a fast halo coronal mass ejection (CME) occurred on 2006 December 13, accompanied by a high flux of energetic particles recorded both in near-Earth space and at ground level. Our purpose is to provide evidence of flare acceleration in a major solar energetic particle (SEP) event. We first present observations from ACE/EPAM, GOES, and the Apatity neutron monitor. It is found that the initial particle release time coincides with the flare emission and that the spectrum becomes softer and the anisotropy becomes weaker during particle injection, indicating that the acceleration source changes from a confined coronal site to a widespread interplanetary CME-driven shock. We then describe a comprehensive study of the associated flare active region. By use of ... [READ MORE]

Authors: C. Li, Y. Dai, J. -C. Vial, C. J. Owen, S. A. Matthews, Y. H. Tang, C. Fang, and A. N. Fazakerley
Projects:

Publication Status: A&A, in press
Last Modified: 2009-08-26 01:54
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Magnetohydrodynamic oscillations in the solar corona and Earth's magnetosphere: Towards consolidated understanding  

Valery Nakariakov   Submitted: 2016-05-13 03:25

Magnetohydrodynamic (MHD) oscillatory processes in different plasma systems, such as the corona of the Sun and the Earth?s magnetosphere, show interesting similarities and differences, which so far received little attention and remain under-exploited. The successful commissioning within the past ten years of THEMIS, Hinode, STEREO and SDO spacecraft, in combination with matured analysis of data from earlier spacecraft (Wind, SOHO, ACE, Cluster, TRACE and RHESSI) makes it very timely to survey the breadth of observations giving evidence for MHD oscillatory processes in solar and space plasmas, and state-of-the-art theoretical modelling. The paper reviews several important topics, such as Alfv?nic resonances and mode conversion; MHD waveguides, such as the magnetotail, coronal loops, ... [READ MORE]

Authors: V.M. Nakariakov, V. Pilipenko, B. Heilig, P. Jel?nek, M. Karlický, D.Y. Klimushkin, D.Y. Kolotkov, D.-H. Lee, G. Nistic?, T. Van Doorsselaere, G. Verth, I.V. Zimovets
Projects: None

Publication Status: Space Science Reviews, published
Last Modified: 2016-05-14 07:55
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Active region upflows: 1. Multi-instrument observations  

Kamalam Vanninathan   Submitted: 2015-09-21 02:19

Upflows at the edges of active regions (ARs) are studied by spatially and temporally combining multi-instrument observations obtained with EIS/Hinode, AIA and HMI/SDO and IBIS/NSO, to derive their plasma parameters. This information is used for benchmarking data-driven modelling of the upflows (Galsgaard et al., 2015). The studied AR upflow displays blueshifted emission of 5-20 km/s in Fe XII and Fe XIII and its average electron density is 1.8x10^9 cm^3 at 1 MK. The time variation of the density shows no significant change (in a 3sigma error). The plasma density along a single loop drops by 50% over a distance of 20000 km. We find a second velocity component in the blue wing of the Fe XII and Fe XIII lines at 105 km/s. This component is persistent during the whole observing period of 3.5 ... [READ MORE]

Authors: K. Vanninathan, M.S. Madjarska, K. Galsgaard, Z.Huang, J.G. Doyle
Projects: None

Publication Status: Accepted for publication in A&A
Last Modified: 2015-09-23 13:31
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Subject will be restored when possible  

Aveek Sarkar   Submitted: 2007-10-11 02:47

There is a growing body of evidence that the plasma loops seen with current instrumentation (SOHO, TRACE and Hinode) may consist of many subresolution elements or strands. Thus, the overall plasma evolution we observe in these features could be the cumulative result of numerous individual strands undergoing sporadic heating. This paper presents a short (109 cm ≡ 10 Mm) `global loop' as 125 individual strands where each strand is modelled independently by a one-dimensional hydrodynamic simulation. The energy release mechanism across the strands consists of localised, discrete heating events (nano-flares). The strands are ?coupled? together through the frequency distribution of the total energy input to the loop which follows a power law distribution with index α. The location ... [READ MORE]

Authors: Aveek Sarkar, Robert W Walsh
Projects:

Publication Status: ApJ(accepted)
Last Modified: 2008-04-22 16:26
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Subject will be restored when possible  

Ignacio Ugarte-Urra   Submitted: 2007-12-10 09:29

Recent observations of coronal hole areas with the XRT and EIS instruments onboard the Hinode satellite have shown with unprecedented detail the launching of fast, hot jets away from the solar surface. In some cases these events coincide with episodes of flux emergence from beneath the photosphere. In this letter we show results of a 3D numerical experiment of flux emergence from the solar interior into a coronal hole and compare them with simultaneous XRT and EIS observations of a jet-launching event that accompanied the appearance of a bipolar region in MDI magnetograms. The magnetic skeleton and topology that result in the experiment bear a strong resemblance to linear force-fee extrapolations of the SOHO/MDI magnetograms. A thin current sheet is formed at the boundary of the emerging ... [READ MORE]

Authors: F. Moreno-Insertis, K. Galsgaard, I. Ugarte-Urra
Projects: None

Publication Status: ApJL, in press.
Last Modified: 2007-12-10 11:17
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Elemental abundances and temperatures of quiescent solar active region cores from X-ray observations  

Giulio Del Zanna   Submitted: 2014-05-07 02:25

A brief review of studies of elemental abundances and emission measures in quiescent solar active region cores is presented. Hinode EUV Imaging Spectrometer (EIS) observations of strong iron spectral lines have shown sharply peaked distributions around 3 MK. EIS observations of lines emitted by a range of elements have allowed good estimates of abundances relative to iron. However, X-ray observations are required to measure the plasma emission above 3 MK and the abundances of oxygen and neon. We revisit, using up-to-date atomic data, older X-ray observations obtained by a sounding rocket and by the Solar Maximum Mission (SMM) Flat Crystal Spectrometer (FCS). We find that the Fe/O and Fe/Ne ratios are normally increased by a factor of 3.2, compared to the photospheric values. Similar ... [READ MORE]

Authors: Del Zanna, G. and Mason, H.E.
Projects: Solar Max Misson

Publication Status: printed, DOI: 10.1051/0004-6361/201423471
Last Modified: 2014-05-07 06:01
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How Can Active Region Plasma Escape into the Solar Wind from below a Closed Helmet Streamer?  

Cristina H. Mandrini   Submitted: 2014-09-25 12:35

Recent studies show that active-region (AR) upflowing plasma, observed by the EUV-Imaging Spectrometer (EIS), onboard Hinode, can gain access to open-fi eld lines and be released into the solar wind (SW) via magnetic interchange reconnection at magnetic null-points in pseudo-streamer configurations. When only one bipolar AR is present on the Sun and it is fully covered by the separatrix of a streamer, such as AR 10978 in December 2007, it seems unlikely that the upflowing AR plasma can find its way into the slow SW. However, signatures of plasma with AR composition have been found at 1 AU by Culhane et al. (2014, Solar Phys. 289, 3799) apparently originating from the West of AR 10978. We present a detailed topology analysis of AR 10978 and the surrounding large-scale corona based on a ... [READ MORE]

Authors: C.H. Mandrini, F.A. Nuevo, A.M. Vasquez, P. Demoulin, L. van Driel-Gesztelyi, D. Baker, J.L. Culhane, G.D. Cristiani, M. Pick
Projects: None

Publication Status: In press
Last Modified: 2014-09-25 15:58
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Kink oscillations of flowing threads in solar prominences  

Roberto Soler   Submitted: 2011-06-21 04:44

Recent observations by Hinode/SOT show that MHD waves and mass flows are simultaneously present in the fine structure of solar prominences. We investigate standing kink magnetohydrodynamic (MHD) waves in flowing prominence threads from a theoretical point of view. We model a prominence fine structure as a cylindrical magnetic tube embedded in the solar corona with its ends line-tied in the photosphere. The magnetic cylinder is composed of a region with dense prominence plasma, which is flowing along the magnetic tube, whereas the rest of the flux tube is occupied by coronal plasma. We use the WKB approximation to obtain analytical expressions for the period and the amplitude of the fundamental mode as functions of the flow velocity. In addition, we solve the full problem numerically by ... [READ MORE]

Authors: Roberto Soler and Marcel Goossens
Projects: None

Publication Status: Accepted in A&A
Last Modified: 2011-06-21 13:47
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Parallel Evolution of Quasi-separatrix Layers and Active Region Upflows  

Cristina H. Mandrini   Submitted: 2015-07-08 17:11

Persistent plasma upflows were observed with Hinode's EUV Imaging Spectrometer (EIS) at the edges of active region (AR) 10978 as it crossed the solar disk. We analyze the evolution of the photospheric magnetic and velocity fields of the AR, model its coronal magnetic field, and compute the location of magnetic null-points and quasi-sepratrix layers (QSLs) searching for the origin of EIS upflows. Magnetic reconnection at the computed null points cannot explain all of the observed EIS upflow regions. However, EIS upflows and QSLs are found to evolve in parallel, both temporarily and spatially. Sections of two sets of QSLs, called outer and inner, are found associated to EIS upflow streams having different characteristics. The reconnection process in the outer QSLs is forced by a large-scale ... [READ MORE]

Authors: Mandrini, C. H.; Baker, D.; D?moulin, P.; Cristiani, G. D.; van Driel-Gesztelyi, L.; Vargas Dom?nguez, S.; Nuevo, F. A.; V?squez, A. M.; Pick, M.
Projects: None

Publication Status: Accepted Astrophys. J.
Last Modified: 2015-07-10 20:38
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Subject will be restored when possible  

Iain Hannah   Submitted: 2007-12-03 18:23

Aims: Investigate particle acceleration and heating in a solar microflare. Methods: In a microflare with non-thermal emission to remarkably high energies ($>50$ keV), we investigate the hard X-rays with RHESSI imaging and spectroscopy and the resulting thermal emission seen in soft X-rays with Hinode/XRT and in EUV with TRACE. Results: The non-thermal footpoints observed with RHESSI spatially and temporally match bright footpoint emission in soft X-rays and EUV. There is the possibility that the non-thermal spectrum extends down to 4 keV. The hard X-ray burst clearly does not follow the expected Neupert effect, with the time integrated hard X-rays not matching the soft X-ray time profile. So although this is a simple microflare with good X-ray observation coverage it does not fit ... [READ MORE]

Authors: I. G. Hannah, S. Krucker, H. S. Hudson, S. Christe and R. P. Lin
Projects: RHESSI

Publication Status: Accepted by A&A Letters
Last Modified: 2007-12-04 07:38
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Predicting observational signatures of coronal heating by Alfv?n waves and nanoflares  

Patrick Antolin   Submitted: 2008-12-13 01:58

Alfv?n waves can dissipate their energy by means of nonlinear mechanisms, and constitute good candidates to heat and maintain the solar corona to the observed few million degrees. Another appealing candidate is nanoflare reconnection heating, in which energy is released through many small magnetic reconnection events. Distinguishing the observational features of each mechanism is an extremely difficult task. On the other hand, observations have shown that energy release processes in the corona follow a power-law distribution in frequency whose index may tell us whether small heating events contribute substantially to the heating or not. In this work we show a link between the power-law index and the operating heating mechanism in a loop. We set up two coronal loop models: in the ... [READ MORE]

Authors: P. Antolin, K. Shibata, T. Kudoh, D. Shiota, D. Brooks
Projects: None

Publication Status: Published in ApJ 688, 669-682
Last Modified: 2008-12-14 17:43
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Oscillations in a sunspot with light bridges  

Ding Yuan   Submitted: 2014-07-10 12:33

Solar Optical Telescope onboard Hinode observed a sunspot (AR 11836) with two light bridges (LBs) on 31 Aug 2013. We analysed a 2-hour \ion{Ca}{2} H emission intensity data set and detected strong 5-min oscillation power on both LBs and in the inner penumbra. The time-distance plot reveals that 5-min oscillation phase does not vary significantly along the thin bridge, indicating that the oscillations are likely to originate from the underneath. The slit taken along the central axis of the wide light bridge exhibits a standing wave feature. However, at the centre of the wide bridge, the 5-min oscillation power is found to be stronger than at its sides. Moreover, the time-distance plot across the wide bridge exhibits a herringbone pattern that indicates a counter-stream of two running waves ... [READ MORE]

Authors: Ding Yuan, Valery M. Nakariakov, Zhenghua Huang, Bo Li, Jiangtao Su, Yihua Yan, Baolin Tan
Projects: None

Publication Status: ApJ accepted
Last Modified: 2014-07-11 14:34
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Yin Zhang   Submitted: 2008-06-24 01:59

In this letter we report a close relationship between the variations of the transport rate of the magnetic helicity dH/dt and the microwave burst. The latter may be regarded as a prompt signal of non-thermal energetic particles originated from the magnetic reconnection during solar flaring events. We analyze the observations of magnetograms of MDI/SOHO and SOT/Hinode, and the high-cadence microwave observation at 2.84 GHz obtained in Chinese Solar Broadband Radiospectrometer (SRBS/Huairou) of a flare/CME event which occurred in Active Region NOAA 10930 on 2006 December 13. We find that there is a sharp jump of dH/dt around the onset and quench of the microwave burst at the frequency of 2.84 GHz: the rate of dH/dt changes from negative to positive around the start of the ... [READ MORE]

Authors: Y. Zhang., B. L. Tan, and Y. H. Yan
Projects: None

Publication Status: accepted
Last Modified: 2008-06-24 08:00
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Structure of sunspot penumbral filaments: a remarkable uniformity of properties  

Sanjiv Tiwari   Submitted: 2013-07-25 07:24

The sunspot penumbra comprises num