Electron acceleration at coronal and interplanetary shock waves

Coronal mass ejections and flares may generate shock waves travelling through the solar corona from which some are able to enter into the interplanetary space. These shocks manifest themselves in solar and interplanetary type II radio bursts. Their nonthermal radio radiation indicates that electrons are accelerated to suprathermal and/or relativistic velocities at these shocks. As well known by extraterrestrial in-situ measurements supercritical, quasi-parallel, collisionless shocks are accompanied by large amplitude magnetohydrodynamic waves in the upstream region. These waves act as strong magnetic mirrors, at which charged particles can be reflected and accelerated. Thus, thermal electrons gain energy due to multiple reflections between two large amplitude MHD waves and reach suprathermal and relativistic velocities. This mechanism of accelerating electrons is discussed for circumstances in the solar corona and the interplanetary space.