Stellar and Solar Flares: Some Theoretical Problems from Point of View Modern Observations

Abstract

The recent X-ray observations allow to work out a scenario of flares, i.e. their spatial and temporal development. The hard and the hot (main) phases are successively considered. During the hard phase it is difficult to use the accepted concept about the reconnection as a mechanism of primary energy release because it is practically impossible to explain the particle acceleration during ≤ 1 s in the low-lying region of ≤ 108cm in size located in a spot penumbra with the same polarity magnetic field. The thermal waves propagating outward from the region of primary energy release along a large coronal loop are considered in some flares as a probable trigger mechanism for transforming the hard phase into the hot one. The reconnection mechanism is acceptable during a hot phase. Common features of secondary processes in solar and stellar flares allow to understand naturally the origin of the flare optical continuum on red dwarfs.KeywordsCurrent SheetSolar FlareThermal WaveCoronal LoopHard PhaseThese keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.