On electron acceleration at CIR related shock waves

The interaction of fast and slow speed solar wind streams leads to the formation of so-called corotating interaction regions (CIRs) in the heliosphere. These CIRs are often associated with shock waves, at which electrons are accelerated as observed by the Ulysses spacecraft. A correlation between the ratio of energetic electron fluxes at the crossing of CIR related shocks to those in the far upstream region of these shocks and the magnetic field compression of the associated shocks has been revealed by analysing the data of the HISCALE instrument aboard Ulysses. This result can be explained by a model of electron acceleration at shock waves, where the electrons gain energy due to multiple reflections at large amplitude magnetic field fluctuations occurring in the vicinity of the shock transition.