Electron Temperature, Emission Measure, and X-Ray Flux in A2 to X2 X-Ray Class Solar Flares

Feldman, U.; Doschek, G. A.; Behring, W. E.; Phillips, K. J. H.

doi:10.1086/177030

Cited by 108 publications

(120 citation statements)

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“…This is a very reasonable value for a B-class flare, and is in excellent agreement with the temperature obtained from the ratios of the GOES fluxes (Fig. 3), and with the accurate temperatures at flare maximum of similar-class flares obtained by Feldman et al (1996) using the satellite lines observed with the Bragg crystal spectrometer (BCS) on-board Yohkoh. If one assumes that the plasma is uniformly distributed along the line-of-sight, EM h 0.83 < N e > 2 Δ h, where Δ h is the depth of the emission layer (we have assumed N H = 0.83N e considering a fully ionized gas with the relative helium abundance A(He) = 0.1).…”

Section: Flare Loop Top: Em Temperature and Electron Densitiessupporting

confidence: 88%

“…Using a number of EIS emission lines formed over a broad temperature range we showed that the loop-top emission of the main flare loop can be explained with an isothermal temperature of 10 MK, the same temperature obtained from the GOES light curves, and the same obtained by Feldman et al (1996) for flares of similar magnitude using the satellite lines observed by Yohkoh BCS. This suggests that assuming isothermal temperatures is a good approximation for flare loops.…”

Section: Discussionsupporting

confidence: 66%

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The 22 May 2007 B-class flare: new insights fromHinodeobservations

Zanna¹,

Mitra-Kraev²,

Bradshaw

et al. 2010

A&A

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We present multi-wavelength observations of a small B-class flare which occurred on the Sun on 2007 May 22. The observations include data from Hinode, GOES, TRACE and the Nobeyama Radioheliograph. We obtained spatially and spectrally-resolved information from the Hinode EUV Imaging Spectrometer (EIS) during this event. The temporal and temperature coverage of the EIS observations provides new insights into our understanding of chromospheric evaporation and cooling. The flare showed many "typical" features, such as brightenings in the ribbons, hot (10 MK) loop emission and subsequent cooling. We also observed a new feature, strong (up to 170 km s −1 ) blue-shifted emission in lines formed around 2-3 MK, located at the footpoints of the 10 MK coronal emission and within the ribbons. Electron densities at 2 MK in the kernels are high, of the order of 10 11 cm −3 , suggesting a very narrow layer where the chromospheric evaporation occurs. We have run a non-equilibrium hydrodynamic numerical simulation using the HYDRAD code to study the cooling of the 10 MK plasma, finding good agreement between the predicted and observed temperatures, densities and ion populations. Line blending for some potentially useful diagnostic lines for flares, which are observed with Hinode/EIS, is also discussed.

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Section: Flare Loop Top: Em Temperature and Electron Densitiessupporting

confidence: 88%

Section: Discussionsupporting

confidence: 66%

The 22 May 2007 B-class flare: new insights fromHinodeobservations

Zanna¹,

Mitra-Kraev²,

Bradshaw

et al. 2010

A&A

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“…This seems a reasonable temperature for a C class flare (cf. Feldman et al 1996). A detailed analysis of the SDO/AIA observations shows regions close to the loop top with electron temperature (T e ) up to 14 MK.…”

Section: Discussionmentioning

confidence: 97%

SDO AIA and EVE observations and modelling of solar flare loops

Petkaki

Zanna

Mason

et al. 2012

A&A

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We present imaging and spectroscopic observations of an isolated C1-class solar flare, obtained with the Atmospheric Imaging Assembly (AIA) and Extreme ultraviolet Variability Experiment (EVE) on the Solar Dynamics Observatory (SDO). We obtain excellent agreement between the peak flare temperatures estimated using the EVE spectra with those obtained from GOES and, most importantly, from the ratio of the 94 Å and 131 Å AIA channels, which are found to be dominated by Fe xviii and Fe xxi. These results confirm that these two AIA bands can be reliably used to provide temperature diagnostics for the peak and gradual phases of solar flares. The flare kernels, probable sources of chromospheric evaporation, are seen as strong localised emission in the AIA bands at the footpoints of flare loops. The flare loops are close to isothermal during the gradual phase. We have run several hydrodynamic simulations (using the HYDRAD code) to study the cooling of the flare loops. We find good overall agreement between observed and predicted electron temperatures and densities when a gradual increase and decrease of the heating is assumed.

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“…Brosius & Holman (2009) detected Fe xix emission (8 × 10 6 K) in a microflare in an active region. Scaling laws of the flare peak temperature and emission measure have been determined (Feldman et al 1996;Shibata & Yokoyama 1999), implying that different scales of flares are produced by the same mechanism. If the relationship could be extended to a lower emission measure, small events are expected to show a low temperature.…”

Section: Discussionmentioning

confidence: 98%

Evolution of microflares associated with bright points in coronal holes and in quiet regions

Kamio

Curdt

Teriaca

et al. 2011

A&A

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Aims. We aim to find similarities and differences between microflares at coronal bright points found in quiet regions and coronal holes, and to study their relationship with large scale flares. Methods. Coronal bright points in quiet regions and in coronal holes were observed with Hinode/EIS using the same sequence. Microflares associated with bright points are identified from the X-ray lightcurve. The temporal variation of physical properties was traced in the course of microflares.Results. The lightcurves of microflares indicated an impulsive peak at hot emission followed by an enhancement at cool emission, which is compatible with the cooling model of flare loops. The density was found to increase at the rise of the impulsive peak, supporting chromospheric evaporation models. A notable difference is found in the surroundings of microflares; diffuse coronal jets are produced above microflares in coronal holes while coronal dimmings are formed in quiet regions. Conclusions. The microflares associated with bright points share common characteristics to active region flares. The difference in the surroundings of microflares are caused by open and closed configurations of the pre-existing magnetic field.

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Electron Temperature, Emission Measure, and X-Ray Flux in A2 to X2 X-Ray Class Solar Flares

Cited by 108 publications

References 0 publications

The 22 May 2007 B-class flare: new insights fromHinodeobservations

The 22 May 2007 B-class flare: new insights fromHinodeobservations

SDO AIA and EVE observations and modelling of solar flare loops

Evolution of microflares associated with bright points in coronal holes and in quiet regions

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