Electron acceleration at a high beta and low Mach number rippled shock

Electron acceleration in a high plasma beta and low Mach number quasiperpendicular shock is investigated by using two-dimensional full particle-in-cell simulation. Although efficient shock drift acceleration followed by reflection was observed in the previous one-dimensional simulation, no reflected electrons are found due to the effect of shock surface rippling for the particular parameters examined here. Structure of the shock transition region is complex in spite of the high beta and low Mach number situation. In addition to the ion scale fluctuations including the ripple, electron scale fluctuations are also recognized. Among these, downstream fluctuations are dominated by Alfvén ion cyclotron instability, the fluctuations in the foot are due to modified two-stream instability. Electron distribution function in the transition region indicates non-thermal nature. The energy gained by the non-thermal electrons is not explained merely by the shock drift acceleration, implying the importance of local wave- particle interactions.