Flares of Red Dwarf Stars and Solar Activity

Abstract

The UV Cet-type star flares and the chromospheric flares of the Sun have many important common features. Both types of events are very transient; they occupy only small parts of the stellar surfaces; in both cases the optical as well as the radio emissions of the flares have strong similarities in temporal and spectral characteristics. Evaluations of electron temperatures, electron densities and the general character of mass motions within radiating gas in the stellar flares also display similarities to solar flares. The solar and stellar atmospheres where the flares develop have many important common characteristics too: the existence of hot chromospheres and coronas above much colder photospheres, the absence of noticeable dust envelopes, the photospheres patched with dark short-lived spots, and some periodicity in spot appearance over several years. The facts permit one to identify the processes which take place during separate solar and stellar flares and which are responsible for the solar and stellar activities in total. From this point of view some general problems of physics and evolution of red-dwarf flare stars are discussed.