Study of particle acceleration processes at collisionless shocks via next-generation and first-principle particle simulations

为了研究垂直激波的非平稳性，进行了大规模的二维全粒子模拟。结果表明，激波锋面的微观不稳定性决定了自整改的持续和缺失。当电磁哨声模波被修正的双流不稳定性强烈激发时，入射离子和反射离子都被强烈散射，激波重构消失。另一方面，当静电波被弱激发或不存在微不稳定性时，反射离子表现出相干行为，激波重塑是持久的。然而，在这种情况下，由于激波前沿的波动，重整期基本上被改变了。模拟结果表明，电子尺度的微不稳定性和离子尺度的激波阵面波纹之间的跨尺度耦合影响着激波的结构和动力学。

Large-scale two-dimensional full particle-in-cell simulations are carried out for studying non-stationarity of perpendicular shocks. It is confirmed that the persistence and absence of the self-reformation is controlled by micro-instabilities at the shock front. When electromagnetic whistler mode waves are strongly excited by the modified two-stream instability, both incoming and reflected ions are strongly scattered and the shock reformation becomes absent. On the other hand, when electrostatic waves are weakly excited or there is no micro-instabilities, reflected ions show a coherent behavior and the shock reformation is persistent. In this case, however, the reformation period is modified essentially due to the shock front ripples. The present simulation result suggests that the structure and dynamics of shocks are affected by the cross-scale coupling between electron-scale micro-instabilities and ion-scale shock-front ripples.