Electron acceleration at coronal shock waves

R. Miteva, G. Mann

Astrophysikalisches Institut Potsdam, An der Sternwarte 16, D-14482 Potsdam, Germany

In the solar corona shock waves are able to accelerate electrons, observed in the solar radio radiation as the well-known type II bursts. From in-situ measurements, at CIR-related shocks in the interplanetary space, it is evident that shock waves with attached whistler packets in their upstream region, preferably accelerate electrons. Motivated by these observations and assuming that the basic physical mechanisms at all collisionless shocks should be the same, we study here the resonant interaction of the electrons with such whistler waves. The model explains also the self-generation of the whistlers by resonant interaction with the coming toward the shock front and subsequently accelerated protons. After that, the incoming electrons will also interact resonantly with the whistler wave field and gain energy from it, within just several whistler periods. Hence, the kinetic energy of the protons is transferred to the electrons via the whistler wave packets. The proposed here model accounts for the more realistic quasi-perpendicular shock configuration, i.e., the angle $\theta_{\rm B,n}$ between the upstream magnetic field and the shock normal is taken to be 45$^\circ$-80$^\circ$, in contrast to previous models (e.g., shock-drift acceleration), that need a nearly perpendicular (i.e., $\theta_{\rm B,n} \approx 90^\circ$) shock geometry. The proposed mechanism for electron acceleration can be applied also to other shock configurations in space plasmas.