Non-thermal particles in the solar atmosphere during flare developments and in the absence of flares

Abstract

Non-thermal particles play a major role in the active Sun since they contain a large amount of the energy released during flares and since dekakeV electrons are produced in the absence of flares in association with active regions. These particles are detected either in the interplanetary space or through the radiations they produce in the solar atmosphere during flares (radio, X-ray/γ-ray bursts) and outside flares (e.g. radio noise storms). We focus on the particles interacting at the Sun. After a brief discussion on emission processes, we discuss some evidences for the fragmentation of the non- thermal energy release during flares and present some observations relevant to the onset of noise storms. New results obtained on the more energetic flares are then summarized: relative amount of accelerated electrons and ions, particle transport from the acceleration site to the emitting regions, hard X-ray and γ-ray coronal contributions from partially trapped particles, high energy (≥ 10 MeV) radiation from relativistic electrons and 100 MeV-1 GeV ions.