Behavior of the flare-produced coronal MHD wavefront and the occurrence of type II radio bursts

摘要: The propagation of the weak MHD fast-mode shock emitted into corona by flares at their explosive phase is computer-simulated. It shown as result that wave refracted towards low Alfven velocity regions pre-existing in corona, and strength shock, which otherwise weak, drastically enhanced on encountering low- VA due to focussing effect refraction also lowered such regions. expected electron acceleration takes place a drastic strengthening leading local excitation plasma waves eventually occurrence radio bursts locations. Such locations enhancement, when computed using HAO realistic models coronal density magnetic field day certain type II burst events, actually coincide roughly with observed positions bursts. Peculiar configurations sources well even beyond horizon responsible flare are explained consistently large scale enhancement global distribution corona. A unified interpretation given for Moreton's phenomena, relation our disturbance other flare-associated dynamical phenomena discussed.