Shock accelerated electrons in the corona

During the event on July 9, 1996 a solar type II radio burst has been recorded by the radio spectralpolarimeter (40-800 MHz) of the Astrophysikalisches Institut Potsdam at 300 MHz on 9:10:54 UT. It was accompanied with type III radio bursts starting below the frequency of the fundamental emission band of the type II burst. Simultaneously, the COSTEP instrument aboard SOHO has measured enhanced electron fluxes up to 3 MeV. This indicates that a shock wave travelling upwards through the corona with a velocity of 1400 km/s was able to produce highly energetic electrons. A mechanism of electron acceleration up to relativistic energies is presented and compared with the observational data. It is well-known that quasi-parallel shocks in space plasmas are accompanied with large amplitude MHD waves in the up-and downstream region. These waves can act as magnetic mirrors at which charged particles can be reflected and accelerated. Thus, thermally distributed electrons gain energy due to multiple reflections at these MHD waves.