Electron Injection at High Mach Number Quasi-perpendicular Shocks: Surfing and Drift Acceleration
Electron Injection at High Mach Number Quasi-perpendicular Shocks: Surfing and Drift Acceleration
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DOI：
10.1086/513599
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发表时间：
2006-12
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影响因子：
--
通讯作者：
T. Amano;M. Hoshino
中科院分区：
文献类型：
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作者：
T. Amano;M. Hoshino
采用一维电磁粒子池模拟方法研究了高马赫数、无碰撞、准垂直激波下的电子注入过程。我们发现高能电子的产生分两个步骤：(1)在激波过渡区前缘通过激波冲浪加速使电子几乎垂直于局部磁场加速，(2)这些预加速电子通过激波漂移加速进一步加速。结果，高能电子被优先反射回上游。激波加速度为反射提供了足够的能量。因此，它不仅对充能过程本身很重要，而且对触发二次加速也很重要。基于仿真结果，我们还建立了两步加速机理的理论模型，该模型可以预测后续扩散冲击加速过程的喷射效率。我们表明，在该模型中得到的注入效率与钱德拉x射线观测SN 1006得到的值吻合得很好。在典型的超新星残余激波中，通过这种机制注入的高能电子可以自我产生上游的alfvsamn波，这些波将高能电子本身散射出去。
The process of electron injection at high Mach number, collisionless, quasi-perpendicular shock waves is investigated by means of one-dimensional electromagnetic particle-in-cell simulations. We find that energetic electrons are generated in two steps: (1) electrons are accelerated nearly perpendicular to the local magnetic field by shock surfing acceleration at the leading edge of the shock transition region, and (2) these preaccelerated electrons are further accelerated by shock drift acceleration. As a result, energetic electrons are preferentially reflected back upstream. Shock surfing acceleration provides sufficient energy for the reflection. Therefore, it is important not only for the energization process itself, but also for triggering the secondary acceleration. We also present a theoretical model of the two-step acceleration mechanism, based on the simulation results, that can predict the injection efficiency for a subsequent diffusive shock acceleration process. We show that the injection efficiency obtained in the present model agrees well with the value obtained from Chandra X-ray observations of SN 1006. At typical supernova remnant shocks, energetic electrons injected by this mechanism can self-generate upstream Alfvén waves, which scatter the energetic electrons themselves.