[P-EM17] 宇宙プラズマ理論・シミュレーション

[PEM17-P06] Electron acceleration efficiency at quasi-perpendicular shocks:
Dependence on shock angle and Alfven Mach number

*大塚 史子¹、松清 修一¹、岡 光夫² (1.九州大学大学院総合理工学研究院、2.カリフォルニア大学バークレー校)

Collisionless shock is thought to be an efficient accelerator of charged particles in space. We have studied electron acceleration mechanism at quasi-perpendicular collisionless shocks by performing 1D particle-in-cell (PIC) simulations. It is found that electrons are efficiently accelerated by the electrostatic field of phase standing whistler waves locally excited in the foot of the supercritical quasi-perpendicular shock. In this study, we have extended our PIC simulations over a wide Alfven Mach numbers range from 3 to 8 and shock normal-magnetic field angles from 65 to 85 degrees, to discuss the electron acceleration efficiency depending on the shock parameters. We investigate the electron acceleration efficiencies such as the density ratio of non-thermal to thermal populations and the maximum attained energy. Then, we discuss how they are related to the so-called whistler critical Mach number. We also discuss the effect of shock nonstationarity on the electron acceleration mechanism.