Coronal Composition above the Solar Equator and the North Pole as Determined from Spectra Acquired by the SUMER Instrument on<i>SOHO</i>

Feldman, U.; Schühle, U.; Widing, K. G.; Laming, J. M.

doi:10.1086/306195

Cited by 134 publications

(159 citation statements)

References 27 publications

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“…A similar result was found by Feldman et al (1998) from off-limb SOHO / SUMER observations of a quiescent streamer. Mohan et al (2000) used off-limb SOHO / SUMER observations above an active region to find a FIP bias of 2-3 in the S/Si abundance.…”

Section: Relative Abundancessupporting

confidence: 88%

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

Zanna¹

2012

A&A

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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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Section: Relative Abundancessupporting

confidence: 88%

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

Zanna¹

2012

A&A

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“…However, many previous analyses of off-limb spectra have successfully used the longer wavelength O VI lines to measure the composition of the corona (e.g., Feldman et al 1998). Muglach et al (2010) compared the long-wavelength O VI lines observed with SUMER and the short-wavelength O VI lines observed with EIS and found that their intensities could not be reconciled.…”

Section: Appendix a O VI Intensities In The Quiet Sunmentioning

confidence: 99%

Transition Region Abundance Measurements During Impulsive Heating Events

Warren

Brooks

Doschek

et al. 2016

ApJ

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It is well established that elemental abundances vary in the solar atmosphere and that this variation is organized by first ionization potential (FIP). Previous studies have shown that in the solar corona, low-FIP elements such as Fe, Si, Mg, and Ca, are generally enriched relative to high-FIP elements such as C, N, O, Ar, and Ne. In this paper we report on measurements of plasma composition made during impulsive heating events observed at transition region temperatures with the Extreme Ultraviolet Imaging Spectrometer (EIS) on Hinode. During these events the intensities of O IV, V, and VI emission lines are enhanced relative to emission lines from Mg V, VI, and VII and Si VI and VII, and indicate a composition close to that of the photosphere. Long-lived coronal fan structures, in contrast, show an enrichment of low-FIP elements. We conjecture that the plasma composition is an important signature of the coronal heating process, with impulsive heating leading to the evaporation of unfractionated material from the lower layers of the solar atmosphere and higher-frequency heating leading to long-lived structures and the accumulation of low-FIP elements in the corona.

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“…Ahmad & Withbroe 1997;Feldman et al 2000). The elemental composition in the coronal layers of coronal holes as compared to that in the normal quiet Sun (which in the following we simply refer to as quiet Sun) has been studied by Feldman et al (1998). Tu et al (1998) derived ion temperatures in a polar coronal hole from line width measurements.…”

Section: Introductionmentioning

confidence: 99%

Properties of ultraviolet lines observed with the Coronal Diagnostic Spectrometer (CDS/SOHO) in coronal holes and the quiet Sun

Stucki

Solanki

Pike

et al. 2002

A&A

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Abstract.We present an analysis of 14 ultraviolet emission lines belonging to different atoms and ions observed inside polar coronal holes and in the normal quiet Sun. The observations were made with the Coronal Diagnostic Spectrometer (CDS) onboard the Solar and Heliospheric Observatory (SOHO). This study extends previous investigations made with the Solar Ultraviolet Measurements of Emitted Radiation (SUMER) spectrometer to higher temperatures. We compare line intensities, shifts and widths in coronal holes with the corresponding values obtained in the quiet Sun. While all lines formed at temperatures above 7 × 10 5 K show clearly the presence of the hole in their intensities, differences in line width are more subtle, with cooler lines being broader in coronal holes, while hotter lines tend to be narrower. According to the present data all lines are blueshifted inside the coronal hole compared to the normal quiet Sun. Almost all the lines formed between 80 000 K and 600 000 K (i.e. transition-region lines) show a correlation between blueshifts and brightness within coronal holes. This is in agreement with the conclusion reached by Hassler et al. (1999) that the fast solar wind emanates from the network and supports our previous study (Stucki et al. 2000b). For coronal lines, this trend seems to be reversed.

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Coronal Composition above the Solar Equator and the North Pole as Determined from Spectra Acquired by the SUMER Instrument onSOHO

Cited by 134 publications

References 27 publications

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

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

Transition Region Abundance Measurements During Impulsive Heating Events

Properties of ultraviolet lines observed with the Coronal Diagnostic Spectrometer (CDS/SOHO) in coronal holes and the quiet Sun

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