Plasma heating to super-hot temperatures (>30 MK) in the August 9, 2011 solar flare

I. N. Sharykin, A. B. Struminskii, I. V. Zimovets

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16 Scopus citations


We investigate the August 9, 2011 solar flare of X-ray class X6.9, the “hottest” flare from 2000 to 2012, with a peak plasma temperature according to GOES data of ≈32.5 MK. Our goal is to determine the cause of such an anomalously high plasma temperature and to investigate the energy balance in the flare region with allowance made for the presence of a super-hot plasma (>30 MK). We analyze the RHESSI, GOES, AIA/SDO, and EVE/SDO data and discuss the spatial structure of the flare region and the results of our spectral analysis of its X-ray emission. Our analysis of the RHESSI X-ray spectra is performed in the one-temperature and two-temperature approximations by taking into account the emission of hot (∼20 MK) and super-hot (∼45 MK) plasmas. The hard X-ray spectrum in both models is fitted by power laws. The observed peculiarities of the flare are shown to be better explained in terms of the two-temperature model, in which the super-hot plasma is located at the flare loop tops (or in the magnetic cusp region). The formation of the super-hot plasma can be associated with its heating through primary energy release and with the suppression of thermal conduction. The anomalously high temperature (33 MK according to GOES) is most likely to be an artefact of the method for calculating the temperature based on two-channel GOES measurements in the one-temperature approximation applied to the emission of a multi-temperature flare plasma with a minor contribution from the low-temperature part of the differential emission measure.

Original languageEnglish (US)
Pages (from-to)53-66
Number of pages14
JournalAstronomy Letters
Issue number1-2
StatePublished - 2015
Externally publishedYes

All Science Journal Classification (ASJC) codes

  • Astronomy and Astrophysics
  • Space and Planetary Science


  • X-ray emission
  • accelerated electrons
  • solar flares


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