Solar Flare Ion Temperatures

Abstract

This paper proposes that the ion temperature is several times the local electron temperature in the hot onset phase and at the above-the-loop region of solar flares. The paper considers: the evidence of spectral line Doppler widths ("non-thermal" broadening); evidence for "universal" ion and electron temperature increase scaling relations for magnetic reconnection in the solar wind, Earth's magnetopause, Earth's magnetotail and numerical simulations; and thermal equilibration times for onset and above-the-loop densities, which are much longer than previous estimates based on soft X-ray flare loops. We conclude that the ion temperature is likely to reach 60 MK or greater and that it may represent a substantial part of spectral line widths, significantly contributing to solving the long-standing issue of the excess nonthermal broadening in flare lines.

Accepted by ApJ Letters

References in corpus (6)

• The role of three-dimensional transport in driving enhanced electron acceleration during magnetic reconnection
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• Solar off-limb line widths: Alfven waves, ion-cyclotron waves, and preferential heating
• The Onset of Ion Heating During Magnetic Reconnection with a Strong Guide Field
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Cited by in corpus (1)

• The Maximum Particle Energy Gain During Magnetic Reconnection