SOLAR FLARE ELEMENT ABUNDANCES FROM THE SOLAR ASSEMBLY FOR X-RAYS (SAX) ON<i>MESSENGER</i>

Dennis, B. R.; Phillips, K. J. H.; Schwartz, R. A.; Tolbert, A. K.; Starr, R.; Nittler, L. R.

doi:10.1088/0004-637x/803/2/67

Cited by 40 publications

(53 citation statements)

References 33 publications

(65 reference statements)

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“…The exact nature of the FIP effect in flare plasmas is still being actively discussed by several authors. For Si (FIP = 8.2 eV), a recent analysis of RESIK observations (Sylwester et al 2015) indicate no enhancement over photospheric, while for Fe (FIP = 7.9 eV), Dennis et al (2015) from X-ray spectra found only a modest enhancement over photospheric and Warren (2014) using extreme ultraviolet spectra found none at all. This possibly indicates that the boundary between high-FIP and low-FIP elements is less than 10 eV.…”

Section: Discussionmentioning

confidence: 93%

THE X-RAY LINE FEATURE AT 3.5 KeV IN GALAXY CLUSTER SPECTRA

Phillips

Sylwester

2015

ApJ

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Recent work by Bulbul et al. and Boyarsky et al. has suggested that a line feature at ∼3.5 keV in the X-ray spectra of galaxy clusters and individual galaxies seen with XMM-Newton is due to the decay of sterile neutrinos, a dark matter candidate. This identification has been criticized by Jeltema & Profumo on the grounds that model spectra suggest that atomic transitions in helium-like potassium (K XVIII) and chlorine (Cl XVI) are more likely to be the emitters. Here it is pointed out that the K XVIII lines have been observed in numerous solar flare spectra at high spectral resolution with the RESIK crystal spectrometer and also appear in Chandra HETG spectra of the coronally active star σ Gem. In addition, the solar flare spectra at least indicate a mean coronal potassium abundance, which is a factor between 9 and 11 higher than the solar photospheric abundance. This fact, together with the low statistical quality of the XMM-Newton spectra, completely account for the ∼3.5 keV feature and there is therefore no need to invoke a sterile neutrino interpretation of the observed line feature at ∼3.5 keV.

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Section: Discussionmentioning

confidence: 93%

THE X-RAY LINE FEATURE AT 3.5 KeV IN GALAXY CLUSTER SPECTRA

Phillips

Sylwester

2015

ApJ

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“…We treat optically thick radiation in the chromosphere with the recipes of Carlsson & Leenaarts (2012). We adopt the photospheric abundances of Asplund et al (2005), as some recent evidence indicates that flares are photospheric in composition (Warren 2014), although there is also evidence to the contrary (Dennis et al 2015;Doschek et al 2015b). …”

Section: Modelingmentioning

confidence: 99%

Transition Region and Chromospheric Signatures of Impulsive Heating Events. Ii. Modeling

Reep

Warren

Crump

et al. 2016

ApJ

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Results from the Solar Maximum Mission showed a close connection between the hard X-ray (HXR) and transition region (TR) emission in solar flares. Analogously, the modern combination of RHESSI and IRIS data can inform the details of heating processes in ways that were never before possible. We study a small event that was observed with RHESSI, IRIS, SDO, and Hinode, allowing us to strongly constrain the heating and hydrodynamical properties of the flare, with detailed observations presented in a previous paper. Long duration redshifts of TR lines observed in this event, as well as many other events, are fundamentally incompatible with chromospheric condensation on a single loop. We combine RHESSI and IRIS data to measure the energy partition among the many magnetic strands that comprise the flare. Using that observationally determined energy partition, we show that a proper multithreaded model can reproduce these redshifts in magnitude, duration, and line intensity, while simultaneously being well constrained by the observed density, temperature, and emission measure. We comment on the implications for both RHESSI and IRIS observations of flares in general, namely that: (1) a single loop model is inconsistent with long duration redshifts, among other observables; (2) the average time between energization of strands is less than 10 s, which implies that for a HXR burst lasting 10 minutes, there were at least 60 strands within a single IRIS pixel located on the flare ribbon; (3) the majority of these strands were explosively heated with an energy distribution well described by a power law of slope »-1.6; (4) the multi-stranded model reproduces the observed line profiles, peak temperatures, differential emission measure distributions, and densities.

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“…Dennis et al (2015), Fludra & Schmelz (1999), and Warren (2014), for example, found enrichments of 1.66 ± 0.34, 1.4 ± 0.4, and 1.17 ± 0.22, respectively, of high-temperature Fe lines observed in a large sample of solar flares. Sylwester et al (2015) derived abundances close to photospheric for hightemperature Si, Ar, and S lines observed during flares.…”

Section: Introductionmentioning

confidence: 96%

“…Dennis et al (2015) and Doschek et al (2015), for example, find that Ca is enriched at all times during flares. Sylwester et al (2015) find evidence for a similar enrichment in K emission.…”

Section: Introductionmentioning

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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SOLAR FLARE ELEMENT ABUNDANCES FROM THE SOLAR ASSEMBLY FOR X-RAYS (SAX) ONMESSENGER

Cited by 40 publications

References 33 publications

THE X-RAY LINE FEATURE AT 3.5 KeV IN GALAXY CLUSTER SPECTRA

THE X-RAY LINE FEATURE AT 3.5 KeV IN GALAXY CLUSTER SPECTRA

Transition Region and Chromospheric Signatures of Impulsive Heating Events. Ii. Modeling

Transition Region Abundance Measurements During Impulsive Heating Events

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