Hemispheric sunspot numbers 1874 - 2020 |
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Astrid Veronig Submitted: 2021-07-22 01:46
Previous studies show significant north-south asymmetries for various features and indicators of solar activity. These findings suggest some decoupling between the two hemispheres over the solar cycle evolution, which is in agreement with dynamo theories. For the most important solar activity index, the sunspot numbers, so far only limited data are available for the two hemispheres independently.
The aim of this study is to create a continuous series of daily and monthly hemispheric sunspot numbers (HSNs) from 1874 to 2020, which will be continuously expanded in the future with the HSNs provided by SILSO.
Based on the available daily measurements of hemispheric sunspot areas from 1874 to 2016 from Greenwich Royal Observatory and National Oceanic and Atmospheric Administration (NOAA), we derive the relative fractions of the northern and southern activity. These fractions are applied to the international sunspot number (ISN) to derive the HSNs. This method and obtained data are validated against published HSNs for the period 1945–2004 and those provided by SILSO for 1992 to 2020.
We provide a continuous data series and catalogue of daily, monthly mean, and 13-month smoothed monthly mean HSNs for the time range 1874–2020 - fully covering solar cycles 12 to 24 - that are consistent with the newly calibrated ISN (Clette et al. 2014). Validation of the reconstructed HSNs against the direct data available since 1945 reveals a high level of consistency, with Pearson correlation coefficients of r = 0.94 (0.97) for the daily (monthly mean) data. The cumulative hemispheric asymmetries for cycles 12–24 give a mean value of 16%, with no obvious pattern in north–south predominance over the cycle evolution. The strongest asymmetry occurs for cycle no. 19, in which the northern hemisphere shows a cumulated predominance of 42%. The phase shift between the peaks of solar activity in the two hemispheres may be up to 28 months, with a mean absolute value over cycles 12–24 of 16.4 months. The phase shifts reveal an overall asymmetry of the northern hemisphere reaching its cycle maximum earlier (in 10 out of 13 cases), with a mean signed phase shift of -7.6 months. Relating the ISN and HSN peak growth rates during the cycle rise phase with the cycle amplitude reveals higher correlations when considering the two hemispheres individually, with r ≈ 0.9.
Our findings provide further evidence that to some degree the solar cycle evolves independently in the two hemispheres, and demonstrate that empirical solar cycle prediction methods can be improved by investigating the solar cycle dynamics in terms of the HSN evolution.
Authors: A.M. Veronig, S. Jain, T. Podladchikova, W. Pötzi, F. Clette
Projects: None
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Publication Status: Astronomy and Astrophyics, in press
Last Modified: 2021-07-22 17:11
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Indications of stellar coronal mass ejections through coronal dimmings |
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Astrid Veronig Submitted: 2021-04-23 08:25
Coronal mass ejections (CMEs) are huge expulsions of magnetized matter from the Sun and stars, traversing space with speeds of millions of kilometres per hour. Solar CMEs can cause severe space weather disturbances and consumer power outages on Earth, whereas stellar CMEs may even pose a hazard to the habitability of exoplanets. Although CMEs ejected by our Sun can be directly imaged by white-light coronagraphs, for stars this is not possible. So far, only a few candidates for stellar CME detections have been reported. Here we demonstrate a different approach that is based on sudden dimmings in the extreme ultraviolet and X-ray emission caused by the CME mass loss. We report dimming detections associated with flares on cool stars, indicative of stellar CMEs, and which are benchmarked by Sun-as-a-star extreme ultraviolet measurements. This study paves the way for comprehensive detections and characterizations of CMEs on stars, which are important factors in planetary habitability and stellar evolution.
Authors: Astrid M. Veronig, Petra Odert, Martin Leitzinger, Karin Dissauer, Nikolaus C. Fleck, Hugh S. Hudson
Projects: SDO-AIA,SDO-EVE
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Publication Status: Nature Astronomy, published
Last Modified: 2021-04-25 15:35
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Spectroscopy and Differential Emission Measure diagnostics of a coronal dimming associated with a fast halo CME |
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Astrid Veronig Submitted: 2019-06-05 04:08
We study the coronal dimming caused by the fast halo CME (deprojected speed v = 1250 km s-1) associated with the C3.7 two-ribbon flare on 2012 September 27, using Hinode/EIS spectroscopy and SDO/AIA Differential Emission Measure (DEM) analysis. The event reveals bipolar core dimmings encompassed by hook-shaped flare ribbons located at the ends of the flare-related polarity inversion line, and marking the footpoints of the erupting filament. In coronal emission lines of log T [K] = 5.8 - 6.3, distinct double component spectra indicative of the superposition of a stationary and a fast up-flowing plasma component with velocities up to 130 km s-1 are observed at regions, which were mapped by the scanning EIS slit close in time of their impulsive dimming onset. The outflowing plasma component is found to be of the same order and even dominant over the stationary one, with electron densities in the upflowing component of 2 x 109 cm-3 at log T [K] = 6.2. The density evolution in core dimming regions derived from SDO/AIA DEM analysis reveals impulsive reductions by 40-50% within ≲10 min, and remains at these reduced levels for hours. The mass loss rate derived from the EIS spectroscopy in the dimming regions is of the same order than the mass increase rate observed in the associated white light CME (1 x 1012 g s-1), indicative that the CME mass increase in the coronagraphic field-of-view results from plasma flows from below and not from material piled-up ahead of the outward moving and expanding CME front.
Authors: Astrid M. Veronig, Peter Gömöry, Karin Dissauer, Manuela Temmer, Kamalam Vanninnathan
Projects: Hinode/EIS,SDO-AIA,SDO-HMI
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Publication Status: Accepted for publication in ApJ
Last Modified: 2019-06-05 14:17
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Genesis and impulsive evolution of the 2017 September 10 coronal mass ejection |
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Astrid Veronig Submitted: 2018-10-24 07:31
The X8.2 event of 10 September 2017 provides unique observations to study the genesis, magnetic morphology and impulsive dynamics of a very fast CME. Combining GOES-16/SUVI and SDO/AIA EUV imagery, we identify a hot (T≈ 10-15 MK) bright rim around a quickly expanding cavity, embedded inside a much larger CME shell (T≈ 1-2 MK). The CME shell develops from a dense set of large AR loops
(≳0.5~Rs), and seamlessly evolves into the CME front observed in LASCO C2.
The strong lateral overexpansion of the CME shell acts as a piston initiating the fast EUV wave. The hot cavity rim is demonstrated to be a manifestation of the dominantly poloidal flux and frozen-in plasma added to the rising flux rope by magnetic reconnection in the current sheet beneath. The same structure is later observed as the core of the white light CME, challenging the traditional interpretation of the CME three-part morphology. The large amount of added magnetic flux suggested by these observations
explains the extreme accelerations of the radial and lateral expansion of the CME shell and cavity, all reaching values of 5-10 km s-2. The acceleration peaks occur simultaneously with the first RHESSI 100-300 keV hard X-ray burst of the associated flare, further underlining the importance of the reconnection process for the impulsive CME evolution.
Finally, the much higher radial propagation speed of the flux rope in relation to the CME shell causes a distinct deformation of the white light CME front and shock.
Authors: Astrid M. Veronig, Tatiana Podladchikova, Karin Dissauer, Manuela Temmer, Daniel B. Seaton, David Long, Jingnan Guo, Bojan Vrsnak, Louise Harra, Bernhard Kliem
Projects: GOES X-rays,SDO-AIA
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Publication Status: ApJ (accepted)
Last Modified: 2018-10-24 10:42
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Plasma diagnostics of coronal dimming events |
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Astrid Veronig Submitted: 2018-02-27 04:58
Coronal mass ejections (CMEs) are often associated with coronal dimmings, i.e. transient dark regions that are most distinctly observed in Extreme Ultra-violet (EUV) wavelengths. Using Atmospheric Imaging Assembly (AIA) data, we apply Differential Emission Measure (DEM) diagnostics to study the plasma characteristics of six coronal dimming events. In the core dimming region, we find a steep and impulsive decrease of density with values up to 50-70%. Five of the events also reveal an associated drop in temperature of 5-25%. The secondary dimming regions also show a distinct decrease in density, but less strong, decreasing by 10-45%. In both the core and the secondary dimming the density changes are much larger than the temperature changes, confirming that the dimming regions are mainly caused by plasma evacuation. In the core dimming, the plasma density reduces rapidly within the first 20-30 min after the flare start, and does not recover for at least 10 hrs later, whereas the secondary dimming tends to be more gradual and starts to replenish after 1-2 hrs. The pre-event temperatures are higher in the core dimming (1.7-2.6 MK) than in the secondary dimming regions (1.6-2.0 MK). Both core and secondary dimmings are best observed in the AIA 211 Å and 193 Å filters. These findings suggest that the core dimming corresponds to the footpoints of the erupting flux rope rooted in the AR, while the secondary dimming represents plasma from overlying coronal structures that expand during the CME eruption.
Authors: Kamalam Vanninathan, Astrid M. Veronig, Karin Dissauer, Manuela Temmer
Projects: SDO-AIA
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Publication Status: Astrophysical Journal, in press
Last Modified: 2018-02-28 13:59
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Reconnection fluxes in eruptive and confined flares and implications for superflares on the Sun |
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Astrid Veronig Submitted: 2017-12-14 08:36
We study the energy release process of a set of 51 flares (32 confined, 19 eruptive) ranging from GOES class B3 to X17. We use Hα filtergrams from Kanzelhöhe Observatory together with SDO HMI and SOHO MDI magnetograms to derive magnetic reconnection fluxes and rates. The flare reconnection flux is strongly correlated with the peak of the GOES 1-8 Å soft X-ray flux (c=0.92, in log-log space), both for confined and eruptive flares. Confined flares of a certain GOES class exhibit smaller ribbon areas but larger magnetic flux densities in the flare ribbons (by a factor of 2). In the largest events, up to 50% of the magnetic flux of the active region (AR) causing the flare is involved in the flare magnetic reconnection. These findings allow us to extrapolate toward the largest solar flares possible. A complex solar AR hosting a magnetic flux of 2 · 1023 Mx, which is in line with the largest AR fluxes directly measured, is capable of producing an X80 flare, which corresponds to a bolometric energy of about 7 · 1032 ergs. Using a magnetic flux estimate of 6 · 1023 Mx for the largest solar AR observed, we find that flares of GOES class ≈X500 could be produced (Ebol ≈ 3 · 1033 ergs). These estimates suggest that the present day's Sun is capable of producing flares and related space weather events that may be more than an order of magnitude stronger than have been observed to date.
Authors: J. Tschernitz, A.M. Veronig, J. Thalmann, J. Hinterreiter, W. Pötzi
Projects: None
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Publication Status: Accepted for publication in ApJ
Last Modified: 2017-12-14 13:38
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Ground-based Observations of the Solar Sources of Space Weather (Invited Review) |
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Astrid Veronig Submitted: 2016-02-09 13:33
Monitoring of the Sun and its activity is a task of growing importance in the frame of space weather research and awareness. Major space weather disturbances at Earth have their origin in energetic outbursts from the Sun: solar flares, coronal mass ejections and associated solar energetic particles. In this review we discuss the importance and complementarity of ground-based and
space-based observations for space weather studies. The main focus is drawn on ground-based observations in the visible range of the spectrum, in particular in the diagnostically manifold Hα spectral line, which enables us to detect and study solar flares, filaments (prominences), filament (prominence) eruptions, and Moreton waves. Existing Hα networks such as the GONG and the Global High-Resolution Hα Network are discussed. As an example of solar observations from space weather research to operations, we present the system of real-time detection of Hα flares and filaments established at Kanzelhöhe Observatory (KSO; Austria) in the frame of the space weather segment of the ESA Space Situational Awareness programme (swe.ssa.esa.int). An evaluation of the system, which is continuously running since July 2013 is provided, covering an evaluation period of almost 2.5 years. During this period, KSO provided 3020 hours of real-time Hα observations at the ESA SWE portal. In total, 824 Hα flares were detected and classified by the real-time detection system, including 174 events of Hα importance class 1 and larger. For the total sample of events, 95% of the automatically determined flare peak times lie within ± 5 min of the values given in the official optical flares reports (by NOAA and KSO), and 76% of the start times. The heliographic positions determined are better than ± 5 degrees. The probability of detection of flares of importance 1 or larger is 95%, with a false alarm rate of 16%. These numbers confirm the high potential of automatic flare detection and alerting from
ground-based observatories.
Authors: Astrid M. Veronig, W. Poetzi
Projects: None
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Publication Status: Accepted for "Ground-based Solar Observations in the Space Instrumentation Era", Proceedings of the Coimbra Solar Physics Meeting 2015, ASP Conference Series, Eds. I. Dorotovic, C. Fischer, and M. Temmer
Last Modified: 2016-02-09 15:00
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Relation between the CME acceleration and the non-thermal flare characteristics |
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Astrid Veronig Submitted: 2012-05-14 04:23
We investigate the relationship between the main acceleration phase of coronal mass ejctions (CMEs) and the particle acceleration in the associated flares as evidenced in RHESSI non-thermal X-rays for a set of 37 impulsive flare-CME events. Both CME peak velocity and peak acceleration yield distinct correlations with various parameters characterizing the flare-accelerated electron spectra. The highest correlation coefficient is obtained for the relation of the CME peak velocity and the total energy in accelerated electrons (c = 0.85), supporting the idea that the acceleration of the CME and the particle acceleration in the associated flare draw their energy from a common source, probably magnetic reconnection in the current sheet behind the erupting structure.
In general, the CME peak velocity shows somewhat higher correlations with the non-thermal flare parameters than the CME peak acceleration, except for the spectral index of the accelerated electron spectrum which yields a higher correlation with the CME peak acceleration (c = -0.6),
indicating that the hardness of the flare-accelerated electron spectrum is tightly coupled to the impulsive acceleration process of the rising CME structure.
We also obtained high correlations between the CME initiation height h0 and the non-thermal flare parameters, with the highest correlation of h0 to the spectral index of flare-accelerated electrons (c = 0.8). This means that CMEs erupting at low coronal heights, i.e. in regions of stronger magnetic fields, are accompanied with flares which are more efficient to accelerate electrons to high energies. In the majority of events (~80%), the non-thermal flare emission starts after the CME acceleration, on average delayed by ~6 min, in line with the standard flare model, where the rising flux rope stretches the field lines underneath until magnetic reconnection sets in. We find that the current sheet length at the onset of magnetic reconnection is 21 ± 7 Mm.
The flare HXR peaks are well synchronized with the peak of the CME acceleration profile, in 75% of the cases they occur within 5 min. Our findings provide strong evidence for the tight coupling between the CME dynamics and the particle acceleration in the associated flare in impulsive events, with the total energy in accelerated electrons being closely correlated to the peak velocity (and thus the kinetic energy) of the CME, whereas the number of electrons acclerated to high energies is decisively related to the CME peak acceleration and the height of the pre-eruptive structure.
Authors: S. Berkebile-Stoiser, A.M. Veronig, B. Bein, M. Temmer
Projects: RHESSI,STEREO
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Publication Status: ApJ, in press
Last Modified: 2012-05-14 12:11
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Plasma diagnostics of an EIT wave observed by Hinode/EIS and SDO/AIA |
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Astrid Veronig Submitted: 2011-11-16 01:46
We present plasma diagnostics of an EIT wave observed with high cadence inHinode/EIS sit-and-stare spectroscopy and SDO/AIA imagery obtained during theHOP-180 observing campaign on 2011 February 16. At the propagating EIT wavefront, we observe downward plasma flows in the EIS Fe XII, Fe XIII, and Fe XVIspectral lines (log T ~ 6.1-6.4) with line-of-sight (LOS) velocities up to 20km s-1. These red-shifts are followed by blue-shifts with upward velocities up to-5 km s-1 indicating relaxation of the plasma behind the wave front. During thewave evolution, the downward velocity pulse steepens from a few km s-1 up to 20km s-1 and subsequently decays, correlated with the relative changes of the lineintensities. The expected increase of the plasma densities at the EIT wavefront estimated from the observed intensity increase lies within the noiselevel of our density diagnostics from EIS XIII 202/203 Å line ratios. Nosignificant LOS plasma motions are observed in the He II line, suggesting thatthe wave pulse was not strong enough to perturb the underlying chromosphere.This is consistent with the finding that no Hα Moreton wave was associatedwith the event. The EIT wave propagating along the EIS slit reveals a strongdeceleration of a ~ -540 m/s2 and a start velocity of v0 ~ 590 km s-1. Thesefindings are consistent with the passage of a coronal fast-mode MHD wave,pushing the plasma downward and compressing it at the coronal base.
Authors: A.M. Veronig, P. Gömöry, I.W. Kienreich, N. Muhr, B. Vrsnak, M. Temmer, H.P. Warren
Projects: Hinode/EIS,SDO-AIA
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Publication Status: ApJ Lett., in press
Last Modified: 2011-11-16 13:19
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Case Study of Four Homologous Large-scale Coronal Waves Observed on 2010 April 28 and 29 |
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Astrid Veronig Submitted: 2011-01-26 09:12
On 2010 April 28 and 29, the Solar TErrestrial Relations Observatory B/Extreme Ultraviolet Imager observed four homologous large-scale coronal waves, the so-called EIT-waves, within 8 hr. All waves emerged from the same source active region, were accompanied by weak flares and faint coronal mass ejections, and propagated into the same direction at constant velocities in the range of ~220-340 km s-1. The last of these four coronal wave events was the strongest and fastest, with a velocity of 337 ± 31 km s-1 and a peak perturbation amplitude of ~1.24, corresponding to a magnetosonic Mach number of Mms ~ 1.09. The magnetosonic Mach numbers and velocities of the four waves are distinctly correlated, suggestive of the nonlinear fast-mode magnetosonic wave nature of the events. We also found a correlation between the magnetic energy buildup times and the velocity and magnetosonic Mach number.
Authors: Kienreich, I. W.; Veronig, A. M.; Muhr, N.; Temmer, M.; Vršnak, B.; Nitta, N.
Projects: STEREO
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Publication Status: ApJ Letts. 727, L43 (2011)
Last Modified: 2011-01-26 12:04
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Multiwavelength imaging and spectroscopy of chromospheric evaporation in an M-class solar flare |
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Astrid Veronig Submitted: 2010-07-08 01:32
We study spectroscopic observations of chromospheric evaporation mass flows in comparison to the energy input by electron beams derived from hard X-ray data for the white-light M2.5 flare of 2006 July 6. The event was captured in high cadence spectroscopic observing mode by SOHO/CDS combined with high-cadence imaging at various wavelengths in the visible, EUV and X-ray domain during the joint observing campaign JOP171. During the flare peak, we observe downflows in the He I and O v lines formed in the chromosphere and transition region, respectively, and simultaneous upflows in the hot coronal Si XII line. The energy deposition rate by electron beams derived from RHESSI hard X-ray observations is suggestive of explosive chromospheric evaporation, consistent with the observed plasma motions. However, for a later distinct X-ray burst, where the site of the strongest energy deposition is exactly located on the CDS slit, the situation is intriguing. The O v transition region line spectra show the evolution of double components, indicative of the superposition of a stationary plasma volume and upflowing plasma elements with high velocities (up to 280 km s-1) in single CDS pixels on the flare ribbon. However, the energy input by electrons during this period is too small to drive explosive chromospheric evaporation. These unexpected findings indicate that the flaring transition region is much more dynamic, complex, and fine-structured than is captured in single-loop hydrodynamic simulations.
Authors: A.M. Veronig, J. Rybak, P. Gömöry, S. Berkebile-Stoiser, M. Temmer, W. Otruba, B. Vrsnak, W. Pötzi, D. Baumgartner
Projects: RHESSI,SoHO-CDS
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Publication Status: Astrophysical Journal (2010, in press)
Last Modified: 2010-07-09 19:22
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First observations of a dome-shaped large-scale coronal EUV wave |
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Astrid Veronig Submitted: 2010-05-26 06:35
We present first observations of a dome-shaped large-scale extreme-ultraviolet coronal wave, recorded by the
Extreme Ultraviolet Imager instrument on board STEREO-B on 2010 January 17. The main arguments that the
observed structure is the wave dome (and not the coronal mass ejection, CME) are (1) the spherical form and
sharpness of the dome?s outer edge and the erupting CME loops observed inside the dome; (2) the low-coronal
wave signatures above the limb perfectly connecting to the on-disk signatures of the wave; (3) the lateral extent
of the expanding dome which is much larger than that of the coronal dimming; (4) the associated high-frequency
type II burst indicating shock formation low in the corona. The velocity of the upward expansion of the wave
dome (v ~ 650 km s-1) is larger than that of the lateral expansion of the wave (v ~ 280 km s-1), indicating
that the upward dome expansion is driven all the time, and thus depends on the CME speed, whereas in the
lateral direction it is freely propagating after the CME lateral expansion stops. We also examine the evolution of
the perturbation characteristics: first the perturbation profile steepens and the amplitude increases. Thereafter, the amplitude decreases with r propto -2.5-0.3, the width broadens, and the integral below the perturbation remains constant. Our findings are consistent with the spherical expansion and decay of a weakly shocked fast-mode MHD wave.
Authors: A. M. Veronig, N. Muhr, I.W. Kienreich, M. Temmer, B. Vrsnak
Projects: STEREO
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Publication Status: Astrophys. J. Letts. 716, L57 (2010)
Last Modified: 2010-05-26 07:17
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Large amplitude oscillatory motion along a solar filament |
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Astrid Veronig Submitted: 2007-07-16 02:43
Large amplitude oscillations of solar filaments is a phenomenon known for more than half a century. Recently, a new mode of oscillations, characterized by periodical plasma motions along the filament axis, was discovered. We analyze such an event, recorded on 23 January 2002 in Big Bear Solar Observatory Hα filtergrams, in order to infer the triggering mechanism and the nature of the restoring force. Motion along the filament axis of a distinct buldge-like feature was traced, to quantify the kinematics of the oscillatory motion. The data were fitted by a damped sine function, to estimate the basic parameters of the oscillations. In order to identify the triggering mechanism, morphological changes in the vicinity of the filament were analyzed. The observed oscillations of the plasma along the filament was characterized by an initial displacement of 24 Mm, initial velocity amplitude of 51 km s-1, period of 50 min, and damping time of 115 min. We interpret the trigger in terms of poloidal magnetic flux injection by magnetic reconnection at one of the filament legs. The restoring force is caused by the magnetic pressure gradient along the filament axis. The period of oscillations, derived from the linearized equation of motion (harmonic oscillator) can be expressed as P=pisqrt{2}L/vAphiapprox4.4L/vAphi, where vAphi =Bphi0/sqrt{mu_0
ho} represents the Alfvén speed based on the equilibrium poloidal field Bphi0. Combination of our measurements with some previous observations of the same kind of oscillations shows a good agreement with the proposed interpretation.
Authors: B. Vrsnak, A.M. Veronig, J.K. Thalmann, T. Zic
Projects: None
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Publication Status: Astron. Astrophys. (in press)
Last Modified: 2007-07-16 12:12
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X-ray sources and magnetic reconnection in the X3.9 flare of 2003 November 3 |
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Astrid Veronig Submitted: 2005-09-30 06:16
Recent RHESSI observations indicate an apparent altitude decrease of flare X-ray loop-top (LT) sources before changing to the commonly observed upward growth of the flare loop system.
We performed a detailed study of the LT altitude decrease for one well observed flare in order to find further hints on the physics of this phenomenon and how it is related to the magnetic reconnection process in solar flares.
RHESSI X-ray source motions in the 2003 November 3, X3.9 flare are studied together with complementary data from SXI, EIT, and Kanzelhöhe Hα . We particularly concentrate on the apparent altitude decrease of the RHESSI X-ray LT source early in the flare and combine kinematical
and X-ray spectral analysis. Furthermore, we present simulations from a magnetic collapsing trap model embedded in a standard 2-D magnetic reconnection model of solar flares.
We find that at higher photon energies the LT source is located at higher altitudes and shows higher downward velocities than at lower energies. The mean downward velocities range from 14 km s-1 in the RHESSI 10-15 keV energy band to 45 km s-1 in the 25-30 keV band. For this flare, the LT altitude decrease was also observed by the SXI instrument with a mean speed of 12 km s-1. RHESSI spectra indicate that during the time of LT altitude decrease the emission of the LT source is thermal bremsstrahlung from a ``superhot'' plasma with temperatures increasing from 35 MK to 45 MK and densities of the order of 1010 cm-3. The temperature does not significantly increase after this early (pre-impulsive superhot LT) phase, whereas the LT densities increase to a peak value of (3-4)cdot 1011 cm-3.}
Modeling of a collapsing magnetic trap embedded in a standard 2D magnetic reconnection model can reproduce the key observational findings in case that the observed emission is thermal bremsstrahlung from the hot LT plasma. This is in accordance with the evaluated RHESSI spectra for this flare.
Authors: A.M. Veronig, M. Karlický, B. Vrsnak, M. Temmer, J. Magdalenic, B.R. Dennis, W. Otruba, W. Poetzi
Projects: RHESSI
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Publication Status: A&A (accepted)
Last Modified: 2005-09-30 06:16
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Multi-wavelength study of coronal waves associated with the CME-flare event of 03 November 2003 |
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Astrid Veronig Submitted: 2005-09-30 03:26
The large flare/CME event that occurred close to the west solar limb on 3 November 2003, launched a large-amplitude large-scale coronal wave which was imaged in Hα and Fe XII 195 A spectral lines, as well as in the soft X-ray and radio wavelength range. The wave excited also a complex decimeter-to-hectometer type II radio burst, revealing the formation of coronal shock(s). The back-extrapolation of the motion of coronal wave signatures and the type II burst sources distinctly marks the impulsive phase of the flare (the hard X-ray peak, drifting microwave burst, and the highest type III burst activity), favoring the flare-ignited wave scenario. On the other hand, the comparison of the kinematics of the CME expansion with the propagation of the optical wave signatures and type II burst sources, shows a severe discrepancy with the CME-driven scenario. However, the CME is quite likely associated with the formation of an upper-coronal shock revealed by the decameter-hectometer
type II burst. Finally, some six minutes after the launch of the first coronal wave, another coronal disturbance was launched, exciting an independent (weak) decimeter-meter range type II burst. The back-extrapolation of this radio emission marks the revival of the hard X-ray burst, and since there was no CME counterpart, it was clearly ignited by the new energy release in the flare.
Authors: B. Vrsnak, A. Warmuth, M. Temmer, A. Veronig, J. Magdalenic, A. Hillaris, M. Karlický
Projects: RHESSI,Soho-EIT,Soho-MDI,Soho-LASCO
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Publication Status: A&A (in press)
Last Modified: 2005-09-30 03:26
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Broadband Metric-Range Radio Emission Associated with a Moreton/EIT Wave |
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Astrid Veronig Submitted: 2005-05-10 07:16
We present the evolution and kinematics of a broadband radio source that propagated collaterally with an Hα/EIT wave, linking it with the type II burst that was excited higher up in the corona. The NRH wave emission extended from the frequency f~327 to f<151 MHz and was considerably weaker than the flare-related type IV burst. The emission centroid propagated at a height of 0-200 Mm above the solar limb and was intensified when the disturbance passed over enhanced coronal structures. We put forward the ad hoc hypothesis that the NRH wave signature is optically thin gyrosynchrotron emission excited by the passage of the coronal MHD fast-mode shock. The identification of radio emission associated with the coronal wave front is important since it offers us new diagnostic information that could provide us with better insight into the physical conditions in the disturbance itself.
Authors:
Vršnak, B., Magdalenić, J., Temmer, M., Veronig, A., Warmuth, A., Mann, G., Aurass, H., Otruba, W.
Projects: None
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Publication Status: ApJ 625, L67 (2005)
Last Modified: 2005-05-10 07:16
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