Generation of highly energetic electrons by shock waves in the solar corona

Abstract

In the solar corona, shock waves are generated by flares or coronal mass ejections. These shock waves are able to accelerate electrons up to high energies as observed by radio astronomical methods in terms of type II radio bursts and by extraterrestrial in situ measurements. A mechanism of electron acceleration acting at small spatial and temporal scales near the shock transition is presented and then compared with measurements of the Comprehensive Suprathermal and Energetic Particle Analyzer (COSTEP) instrument aboard the SOHO spacecraft during a particular solar event. A numerical hybrid simulation performed under typical coronal circumstances shows that strong magnetic field fluctuations appear immediately at the vicinity of the shock transition. Multiple encounters of electrons with such large‐amplitude fluctuations lead to considerable acceleration up to high energies of about 1 MeV.