Benchmarking atomic data for astrophysics:  Fe XVII EUV lines

Zanna, G. Del; Ishikawa, Yasuyuki

doi:10.1051/0004-6361/200911729

Cited by 46 publications

(51 citation statements)

References 30 publications

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“…Evidence was found in a number of cases (Del Zanna 2008a;Del Zanna & Ishikawa 2009) for lines around 250 Å having significantly lower intensities than expected. It is obviously important to attempt measurements of electron temperatures which are independent of any assumption of ionization equilibrium.…”

Section: Discussionmentioning

confidence: 81%

Benchmarking atomic data for astrophysics: Fe VIII EUV lines

Zanna¹

2009

A&A

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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 3s 2 3p 5 3d 2 4 D 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.

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Section: Discussionmentioning

confidence: 81%

Benchmarking atomic data for astrophysics: Fe VIII EUV lines

Zanna¹

2009

A&A

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“…The EUV range is very crowded, and the best way forward is to study clean spectra of different sources. The main hot flare lines have been identified in Del Zanna (2008) and Del Zanna & Ishikawa (2009). An almost pure EIS spectrum containing only transition-region lines was presented by Del Zanna (2009a).…”

Section: Introductionmentioning

confidence: 93%

Benchmarking atomic data for the CHIANTI atomic database: coronal lines observed by Hinode EIS

Zanna¹

2012

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The coronal lines that are observable in the Hinode EUV Imaging Spectrometer (EIS) wavelengths are assessed with new atomic data that have recently become available for a range of important ions. EIS spectral lines are identified based on their spatial variation across different solar regions, their wavelengths, and their intensities. Two off-limb observations are presented, one above an active region, and one in the quiet Sun. The spectra are relatively free of low-temperature lines. Accurate wavelengths and intensities are provided. The observed and predicted line intensities generally agree excellently, once blending is taken into account. The main diagnostics available for measuring the electron density of the solar corona using EIS are highlighted with the use of the emissivity ratio technique. Densities obtained from different ions agree excellently. Most of the previous identifications are confirmed. A considerable number of weaker lines still await identification, however. The approximate formation temperature of the main unidentified lines is provided to aid the identification process. The EIS radiometric calibration appears to be in need of revision. A new quiet-Sun argon/iron relative abundance of 0.16, in line with Galactic measurements, is found. The abundances of sulphur and argon in the "background" unresolved active region emission are found to be lower by a factor of about two at 1.5 MK, and even lower at 3 MK.

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“…We therefore used custom-written software to linearly interpolate the unusable pixels, and visually inspect each single EIS exposure in all channels. We then used custom-written software to rotate each exposure, to correct for the slant of the spectra relative to the axes of the CCD (3.7 ± 0.2 arcsec end-to-end), as found in Del Zanna & Ishikawa (2009). The offset (18 ) between the SW and LW channels in the N-S direction was corrected, leaving a FOV of 120 × 140 .…”

Section: Observations and Analysismentioning

confidence: 99%

SDO AIA and Hinode EIS observations of “warm” loops

Zanna

O’Dwyer

Mason

2011

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We present simultaneous observations of active region "warm" (1 MK) loops using the Solar Dynamics Observatory (SDO) Atmospheric Imaging Assembly (AIA) and Hinode EUV Imaging Spectrometer (EIS). Sample EIS spectra for a loop footpoint and a lop leg region are presented, and are used to describe the spectral lines which contribute to the six AIA EUV channels, both directly and predicted with DEM modeling. We find good overall agreement between observed and predicted count rates for the 131 Å, 193 Å, and 335 Å bands, but highlight a number of problems, partly to be ascribed to inter-calibration issues, partly due to the fact that a large number of lines remain unidentified for the 94 Å, 171 Å, and 211 Å bands. We also found that the 335 Å band is severely affected by cross-talk with the 131 Å band and by second order contributions. We extend our previous work where we highlighted the multi-thermal nature of the SDO AIA bands to show that emission from lines formed at typical transition region temperatures (log T [K] = 5.0-5.8) can be significant for all the EUV channels, and even dominant in some cases. We also assess the possibility of deriving accurate emission measures from the AIA observations. We have found that the inversion of the AIA data to obtain a description of the thermal characteristics of warm loops is unreliable. We highlight the need for further work on the relevant atomic data before the AIA data can be reliably used for plasma diagnostic purposes.

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Benchmarking atomic data for astrophysics: Fe XVII EUV lines

Cited by 46 publications

References 30 publications

Benchmarking atomic data for astrophysics: Fe VIII EUV lines

Benchmarking atomic data for astrophysics: Fe VIII EUV lines

Benchmarking atomic data for the CHIANTI atomic database: coronal lines observed by Hinode EIS

SDO AIA and Hinode EIS observations of “warm” loops

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