Flares on Red Dwarf Stars as a Result of the Dynamical Response of the Chromosphere to the Heating

Abstract

The impulsive hard X-ray, EUV and microwave radio bursts always start at or after the onset of a soft X-ray increase - the main phase of a solar flare - before the Hα flare maximum. This hard phase of a solar flare lasts ~ 100 s and consists of several elementary bursts of 10 s duration. In this time electrons are accelerated up to energy 20-100 keV, then they are injected vertically downwards into denser chromospheric layers. The electron heating as well as the thermal conductivity heating leads to the appearance of the secondary process, in particular, to gasdynamical motions (Kostyuk and Pikel'ner, 1940.