垂直激波条件下能量粒子加速机制的模拟研究

Study of Energetic particle's Acceleration Mechanism at Perpendicular Shock With Particle Simulation Results

在具有湍动的磁场和垂直激波条件下对大量测试粒子的轨迹进行了数值计算,研究了激波强度和粒子初始能量对于粒子穿越激波的平均能量变化的影响,分析了漂移加速(SDA)在不同条件下对粒子加速的贡献,并给出了一个与数值结果相符合的漂移加速理论公式ΔE=amv_iv_(up)(1-1/s).结果表明,加入磁场湍流后,垂直激波条件下粒子仍主要受到漂移加速作用,而基于粒子引导中心的耗散漂移加速理论在此条件下失效.

Large amount of test particles＇ trajectories at perpendicular shock with magnetic turbulence are calculated. And the effect of shock strength and particles＇ initial energy to the average energy change per shock-crossing is also studied. Furthermore, the test particle＇s energy gain from Shock Drift Acceleration （SDA） under different conditions is analysed, too. In addition, a theoretical （1） formula △E=arnvivup（1-1/s） is given for SDA, which agrees very well with our simulation results. The results show that, although magnetic turbulence is included, particles would still be accelerated mainly by SDA at perpendicular shock, while the diffusive shock acceleration, based on the guiding center assumption, is not valid.