THE THERMAL PROPERTIES OF SOLAR FLARES OVER THREE SOLAR CYCLES USING
                    <i>GOES</i>
                    X-RAY OBSERVATIONS

Ryan, Daniel; Milligan, Ryan O.; Gallagher, Peter T.; Dennis, B. R.; Tolbert, A. K.; Schwartz, R. A.; Young, C. A.

doi:10.1088/0067-0049/202/2/11

Cited by 82 publications

(103 citation statements)

References 40 publications

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“…As the flare progresses, the lowest energy bands become dominated by thermal emission. This can be explained by heating of the plasma in the flare loop from 8 MK to 11 MK within 15 s, as derived from GOES observations, using the background subtraction method outlined in Ryan et al (2012). As the plasma reaches greater temperatures, it emits thermal radiation at higher energies.…”

Section: Discussionmentioning

confidence: 99%

Solar flare X-ray source motion as a response to electron spectral hardening

O'Flannagain

Gallagher

Brown

et al. 2013

A&A

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Context. Solar flare hard X-rays (HXRs) are thought to be produced by nonthermal coronal electrons stopping in the chromosphere or remaining trapped in the corona. The collisional thick target model (CTTM) predicts that more energetic electrons penetrate to greater column depths along the flare loop. This requires that sources produced by harder power-law injection spectra should appear further down the legs or footpoints of a flareloop. Therefore, the frequently observed hardening of the injected power-law electron spectrum during flare onset should be concurrent with a descending hard X-ray source. Aims. We test this implication of the CTTM by comparing its predicted HXR source locations with those derived from observations of a solar flare which exhibits a nonthermally-dominated spectrum before the peak in HXRs, known as an early impulsive event.Methods. The HXR images and spectra of an early impulsive C-class flare were obtained using the Ramaty High-Energy Solar Spectroscopic Imager (RHESSI). Images were reconstructed to produce HXR source height evolutions for three energy bands. Spatially integrated spectral analysis was performed to isolate nonthermal emission and to determine the power-law index of the electron injection spectrum. The observed height-time evolutions were then fitted with CTTM-based simulated heights for each energy, using the electron spectral indices derived from the RHESSI spectra. Results. The flare emission was found to be dominantly nonthermal above ∼7 keV, with emission of thermal and nonthermal X-rays likely to be simultaneously observable below that energy. The density structure required for a good match between model and observed source heights agreed with previous studies of flare loop densities. Conclusions. The CTTM has been used to produce a descent of model HXR source heights that compares well with observations of this event. Based on this interpretation, downward motion of nonthermal sources should occur in any flare where there is spectral hardening in the electron distribution during a flare. However, this is often masked by thermal emission associated with flare plasma preheating. To date, flare models that predict transfer of energy from the corona to the chromosphere by means other than a flux of nonthermal electrons do not predict this observed source descent. Therefore, flares such as this will be key in explaining this elusive energy transfer process.

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Section: Discussionmentioning

confidence: 99%

Solar flare X-ray source motion as a response to electron spectral hardening

O'Flannagain

Gallagher

Brown

et al. 2013

A&A

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“…Yashiro et al, 2004). For flares of GOES class C and larger, the rate is even higher with over 2500 events per year during solar maximum (derived from Ryan et al, 2012). The occurrence rate of metric type II bursts (according to the catalogs compiled by NOAA 5 ) ranges from a few events per year during solar minima up to more than 100 bursts during solar maximum.…”

Section: Frequency Of Occurrencementioning

confidence: 99%

“…Saint-Hilaire and Benz, 2005;Mann and Warmuth, 2011;Ryan et al, 2012). 7 This implies that coronal waves represent a non-negligible fraction of the energy released in a solar eruptive event (at least in smaller events).…”

Section: Energeticsmentioning

confidence: 99%

Large-scale Globally Propagating Coronal Waves

Warmuth

2015

Living Rev. Sol. Phys.

168

140

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Large-scale, globally propagating wave-like disturbances have been observed in the solar chromosphere and by inference in the corona since the 1960s. However, detailed analysis of these phenomena has only been conducted since the late 1990s. This was prompted by the availability of high-cadence coronal imaging data from numerous spaced-based instruments, which routinely show spectacular globally propagating bright fronts. Coronal waves, as these perturbations are usually referred to, have now been observed in a wide range of spectral channels, yielding a wealth of information. Many findings have supported the "classical" interpretation of the disturbances: fast-mode MHD waves or shocks that are propagating in the solar corona. However, observations that seemed inconsistent with this picture have stimulated the development of alternative models in which "pseudo waves" are generated by magnetic reconfiguration in the framework of an expanding coronal mass ejection. This has resulted in a vigorous debate on the physical nature of these disturbances. This review focuses on demonstrating how the numerous observational findings of the last one and a half decades can be used to constrain our models of large-scale coronal waves, and how a coherent physical understanding of these disturbances is finally emerging. Article RevisionsLiving Reviews supports two ways of keeping its articles up-to-date:Fast-track revision. A fast-track revision provides the author with the opportunity to add short notices of current research results, trends and developments, or important publications to the article. A fast-track revision is refereed by the responsible subject editor. If an article has undergone a fast-track revision, a summary of changes will be listed here.Major update. A major update will include substantial changes and additions and is subject to full external refereeing. It is published with a new publication number.For detailed documentation of an article's evolution, please refer to the history document of the article's online version at http://dx

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“…Given a well-constrained DEM for a plasma, it is possible to estimate the radiated energy loss rate as follows (e.g., Aschwanden 2005;Ryan et al 2012).…”

Section: Radiative Lossesmentioning

confidence: 99%

INVESTIGATING THE DIFFERENTIAL EMISSION MEASURE AND ENERGETICS OF MICROFLARES WITH COMBINEDSDO/AIA ANDRHESSIOBSERVATIONS

Inglis

Christe

2014

ApJ

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An important question in solar physics is whether solar microflares, the smallest currently observable flare events in X-rays, possess the same energetic properties as large flares. Recent surveys have suggested that microflares may be less efficient particle accelerators than large flares, and hence contribute less non-thermal energy, which may have implications for coronal heating mechanisms. We therefore explore the energetic properties of microflares by combining EUV and X-ray measurements. We present forward-fitting differential emission measure (DEM) analysis of 10 microflares. The fitting is constrained by combining, for the first time, high-temperature Reuven Ramaty High Energy Solar Spectroscopic Imager (RHESSI) observations and flux data from the Solar Dynamics Observatory (SDO) Atmospheric Imaging Assembly (AIA). Two fitting models are tested for the DEM; a Gaussian distribution and a uniform DEM profile. A Gaussian fit proved unable to explain the observations for any of the studied microflares. However, 8 of 10 events studied were reasonably fit by a uniform DEM profile. Hence microflare plasma can be considered to be significantly multi-thermal, and may not be significantly peaked or contain resolvable fine structure, within the uncertainties of the observational instruments. The thermal and non-thermal energy is estimated for each microflare, comparing the energy budget with an isothermal plasma assumption. From the multi-thermal fits the minimum non-thermal energy content was found to average approximately 30% of the estimated thermal energy. By comparison, under an isothermal model the non-thermal and thermal energy estimates were generally comparable. Hence, multi-thermal plasma is an important consideration for solar microflares that substantially alters their thermal and non-thermal energy content.

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THE THERMAL PROPERTIES OF SOLAR FLARES OVER THREE SOLAR CYCLES USING GOES X-RAY OBSERVATIONS

Cited by 82 publications

References 40 publications

Solar flare X-ray source motion as a response to electron spectral hardening

Solar flare X-ray source motion as a response to electron spectral hardening

Large-scale Globally Propagating Coronal Waves

INVESTIGATING THE DIFFERENTIAL EMISSION MEASURE AND ENERGETICS OF MICROFLARES WITH COMBINEDSDO/AIA ANDRHESSIOBSERVATIONS

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