E-Print Archive

There are 3783 abstracts currently viewable.


Search:

Advanced Search
Options
Main Page Add New E-Print Submitter
Information
Feedback
News Help/FAQ About Preferences
Manage Key Phrase
Notification
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 inversion were investigated. DEMs obtained from the XRT bands were also computed and compared to those obtained with EIS. Results: For the active region observations, the observed XRT count rates for most of the channels are in reasonable agreement with those predicted using EIS observations, but are dependent on the elemental abundances chosen. Significant discrepancies between predicted and observed count rates were found and are discussed for the adjacent quiet Sun region and also for the flare. Synthetic spectra and continuum emission contributing to the XRT channels are presented and discussed for the active region, quiet Sun and flare observations.

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
Go to main E-Print page  Edit Entry  Download Preprint  Submitter's Homepage Delete Entry 

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 results are obtained from FCS observations of six quiescent active region cores. The FCS observations also indicate that the emission measure above 3 MK has a very steep negative slope, with very little plasma observed at 5 MK or above.

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
Go to main E-Print page  Edit Entry  Download Preprint  Submitter's Homepage Delete Entry 

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 Å band. We found that the newly identified Fe XIV 93.61 A line is the dominant contribution to the 94 Å band, whenever Fe XVIII is not present. Three methods to estimate the Fe XVIII emission in this band are presented, two using EIS and one directly from the AIA data. Fe XVIII emission is often present in the cores, but we found cases where it is formed at 3 MK and not 7 MK, the temperature of peak ion abundance in equilibrium. The best EIS lines for elemental abundance and DEM analysis are discussed. A new set of abundances for many elements are obtained from EIS observations of hot 3 MK loops. The abundances of the elements with low First Ionisation Potential (FIP), relative to those of the high-FIP elements, are found enhanced by about a factor of three, compared to the photospheric values. A measurement of the path length implies that the absolute abundances of the low-FIP elements are higher than the photospheric values by at least a factor of three. We present a new differential emission measure (DEM) method customised for the AIA bands,to study the thermal structure of ARs at 1'' resolution. It was tested on a few ARs, including one observed during the Hi-C rocket flight. We found excellent agreement between predicted and observed AIA count rates and EIS radiances. We found overall little differences in the AIA and Hi-C 193 Å images of coronal structures, despite the higher Hi-C resolution (0.25''). The Hi-C images and the AIA DEM modelling suggest that some of the cooler loops (below 1 MK) are already resolved by AIA, while the hotter (1.5-2.5 MK) `background' emission is in most places still unresolved even at the Hi-C resolution. This unresolved emission is significantly lower than previously observed with TRACE and the SOHO CDS and Hinode EIS spectrometers. Its enhancement appears to be mostly due to increased iron abundance. We find an ubiquitous presence of emission at different temperatures that is not co-spatial, and suggest that future high-resolution imaging is done with isothermal bands.

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
Go to main E-Print page  Edit Entry  Download Preprint  Submitter's Homepage Delete Entry 

Spectral diagnostics with the SDO EVE flare lines  

Giulio Del Zanna   Submitted: 2013-05-09 04:31

The diagnostic use of the soft X-ray and EUV lines observed with the Solar Dynamics Observatory (SDO) Extreme ultraviolet Variability Experiment (EVE) is discussed. We focus on all the flare lines observed in the 80-640 A range (mainly due to Fe XVIII - Fe XXIV), showing their use to measure temperatures, emission measures, densities, and chemical abundances. We discuss their identification at the EVE resolution, by using the latest atomic data, and by assessing possible sources of blending, taking into account higher-resolution solar spectra. We present observations of four flares, and study in more detail the gradual phase peak of the 7 March 2012 X5.6 flare. Good agreement between observations and theory is found in most cases, and the best lines for diagnostics are recommended. We found reasonable densities (1011.2 cm-3 from Fe XXI lines), but isothermal temperatures (12 MK) lower than those estimated with GOES. We show that EVE can be used to measure relative elemental abundance, and find photospheric argon/iron and calcium/iron abundances. We also show that lines normally formed in the quiet Sun in the low transition region such as O III are the best to study the impulsive phase.

Authors: G. Del Zanna, T.N. Woods
Projects: SDO-EVE

Publication Status: accepted for publication in A&A
Last Modified: 2013-05-09 09:47
Go to main E-Print page  Edit Entry  Download Preprint  Submitter's Homepage Delete Entry 

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 show significant degradation, while that of the long-wavelength (LW) channel shows a significant degradation with time. By the beginning of 2010 the responsivity of the LW channel was already a factor of two or more lower than the values measured on the ground. A first-order correction is proposed. With this correction, the main ratios of lines in the two channels become constant to within a relative 20%, and the He II 256 A radiances over the quiet Sun also become constant over time. This correction removes long-standing discrepancies for a number of lines and ions, in particular those involving the strongest Fe X, Fe XIII, Fe XIV, Fe XVI and Fe XXIV lines, where discrepancies of factors of more than two were found. These results have important implications for various EIS science analyses, in particular for measurements of temperatures, emission measures and elemental abundances.

Authors: G. Del Zanna
Projects: Hinode/EIS

Publication Status: accepted for publication in A&A
Last Modified: 2013-05-09 09:48
Go to main E-Print page  Edit Entry  Download Preprint  Submitter's Homepage Delete Entry 

Benchmarking atomic data for astrophysics: Fe XVII lines  

Giulio Del Zanna   Submitted: 2011-10-07 07:32

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: None

Publication Status: A&A, in press
Last Modified: 2011-10-08 12:25
Go to main E-Print page  Edit Entry  Download Preprint  Submitter's Homepage Delete Entry 

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
Go to main E-Print page  Edit Entry  Download Preprint  Submitter's Homepage Delete Entry 

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
Go to main E-Print page  Edit Entry  Download Preprint  Submitter's Homepage Delete Entry 

The EUV spectrum of the Sun: SOHO CDS NIS irradiances from 1998 until 2010  

Giulio Del Zanna   Submitted: 2011-02-15 05:02

We present extreme-ultraviolet (EUV) irradiances of the Sun taken during the 1998-2010 period from the Solar & Heliospheric Observatory (SOHO) Coronal Diagnostic Spectrometer (CDS) Normal Incidence Spectrograph (NIS). They were obtained from NIS full-Sun radiance observations, and represent the first set of EUV spectral observations spanning a solar cycle. We compare the CDS line irradiances with those obtained from rocket measurements, one that flew in May 1997 and one in April 2008, together with the Thermosphere Ionosphere Mesosphere Energetics Dynamics (TIMED) Solar EUV Experiment (SEE) EUV Grating Spectrograph (EGS) and various historical records. Excellent agreement (to within a relative 20%) is found in most cases, with a few notable exceptions. Lines formed in the transition region show very small changes with the solar cycle, with the exception of the helium lines. The irradiances of lines formed around 1 MK already change during the cycle by a factor ~ 5; for hotter lines (2.5 MK) the variability reaches factors of the order of 40. For lines formed around 1-3 MK, and to a less extent, the helium lines, we find a good linear correlation between CDS irradiances and the 10.7 cm radio flux, although each line has a different coefficient. No correlation is found for the transition-region lines. Significant discrepancies between the observed irradiances and those modelled is found. This confirms the importance in obtaining EUV spectral measurements of the solar irradiance.

Authors: Del Zanna, G. and Andretta,V.
Projects: SoHO-CDS

Publication Status: A&A (accepted)
Last Modified: 2011-02-15 08:58
Go to main E-Print page  Edit Entry  Download Preprint  Submitter's Homepage Delete Entry 

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 which lines are clearly blended in these datasets, and which are reliable for diagnostic purposes.

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

Publication Status: A&A in press
Last Modified: 2009-11-23 13:51
Go to main E-Print page  Edit Entry  Download Preprint  Submitter's Homepage Delete Entry 

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 configuration, are observed for the first time, and are shown to provide a new important diagnostic for measuring the electron temperature in the solar transition region. The temperatures obtained at the base of solar coronal loops are found to be close to the temperature of maximum abundance in ionization equilibrium (log T [K]= 5.4). The assessment of the Fe VII lines was done in conjunction with an assessment of all the strongest cool lines observed with EIS. This spectrum is rich in transition region lines. Some new identifications are presented, in particular for Fe IX. Most of the strongest transitions are identified, however a large number of lines still awaits firm identification.

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

Publication Status: A&A in press
Last Modified: 2009-11-23 13:51
Go to main E-Print page  Edit Entry  Download Preprint  Submitter's Homepage Delete Entry 

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 loops are lower (log T [K]= 5.5) than those predicted by assuming ionization equilibrium (log T [K]= 5.6), however firm measurements will only be possible once better scattering calculations are available, and the EIS radiometric calibration is properly assessed.

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

Publication Status: A&A in press
Last Modified: 2009-11-23 13:51
Go to main E-Print page  Edit Entry  Download Preprint  Submitter's Homepage Delete Entry 

A multi-wavelength study of the compact M1 flare on October 22, 2002  

Giulio Del Zanna   Submitted: 2005-12-05 12:10

In this paper we present a further study of the M1 class flare observed on October 22, 2002. We focus on the SOHO Coronal Diagnostic Spectrometer (CDS) spectral observations performed during a multi-wavelength campaign with TRACE and ground-based instruments (VTT, THEMIS). Strong blue-shifts are observed in the CDS coronal lines in flare kernels during the impulsive phase of this flare. From a careful wavelength calibration we deduce upflows of 140 km s-1 for the Fe~XIX flare emission, with a pattern of progressively smaller flows at lower temperatures. Large line-widths were observed, especially for the Fe XIX line, which indicate the existence of turbulent velocities. The strong upflows correspond to full shifts of the line profiles. These flows are observed at the initial phase of the flare, and correspond to the ``explosive evaporation''. The regions of the blueshifted kernels, a few arc seconds away from the flare onset location, could be explained by the chain reaction of successive magnetic reconnections of growing emerging field line with higher and higher overlying field. This interpretation is evidenced by the analysis of the magnetic topology of the active region using a linear force-free-field extrapolation of THEMIS magnetograms.

Authors: Del Zanna,G., Berlicki,A.,Schmieder,B.,Mason,H.E.
Projects: Soho-CDS,TRACE

Publication Status: Sol. Phys., in press
Last Modified: 2005-12-05 12:10
Go to main E-Print page  Edit Entry  Download Preprint  Submitter's Homepage Delete Entry 


Key
Go to main E-Print pageGo to main E-Print page.
Download PreprintDownload Preprint.
Submitter's HomepageSubmitters Homepage.
Edit EntryEdit Entry.
Delete AbstractDelete abstract.

Abstracts by Author
Response of Hinode XRT to quiet Sun, active region and flare plasma
Elemental abundances and temperatures of quiescent solar active region cores from X-ray observations
The multi-thermal emission in solar active regions
Spectral diagnostics with the SDO EVE flare lines
A revised radiometric calibration for the Hinode/EIS instrument
Benchmarking atomic data for astrophysics: Fe XVII lines
Benchmarking atomic data for the CHIANTI atomic database: coronal lines observed by Hinode EIS
SDO AIA and Hinode EIS observations of `warm' loops
The EUV spectrum of the Sun: SOHO CDS NIS irradiances from 1998 until 2010
Benchmarking atomic data for astrophysics: Fe XVII EUV lines
Benchmarking atomic data for astrophysics: Fe VII and other cool lines observed by Hinode EIS
Benchmarking atomic data for astrophysics: Fe VIII EUV lines
A multi-wavelength study of the compact M1 flare on October 22, 2002

Related Pages
MSU Solar Physics.
Max Millennium Science Mail Archive.
Max Millennium Message of the Day Mail Archive.
Max Millennium Flare Catalog

Archive Maintainer
Alisdair Davey



© 2003 Solar Physics Group - Montana State University