Department of Physics, Chiba University, 1-33 Yayoi-cho, Inage-ku, Chiba 263-8522, Japan.
Phys Rev Lett. 2013 Nov 22;111(21):215003. doi: 10.1103/PhysRevLett.111.215003. Epub 2013 Nov 19.
Electron acceleration associated with various plasma kinetic instabilities in a nonrelativistic shock with very high Alfvén Mach number (M(A)~45) is revealed by means of a two-dimensional fully kinetic particle-in-cell simulation. Electromagnetic (ion Weibel) and electrostatic (ion-acoustic and Buneman) instabilities are strongly activated at the same time in different regions of the two-dimensional shock structure. Relativistic electrons are quickly produced predominantly by the shock surfing mechanism with the Buneman instability at the leading edge of the foot. The energy spectrum has a high-energy tail exceeding the upstream ion kinetic energy accompanying the main thermal population. This gives a favorable condition for the ion-acoustic instability at the shock front, which in turn results in additional energization. The large-amplitude ion Weibel instability generates current sheets in the foot, implying another dissipation mechanism via magnetic reconnection in a three-dimensional shock structure in the very-high-M(A) regime.
通过二维全动力学粒子模拟揭示了在具有极高阿尔芬马赫数（M(A)~45）的非相对论激波中与各种等离子体动力学不稳定性相关的电子加速。在二维激波结构的不同区域中，电磁（离子 Weibel）和静电（离子声波和 Buneman）不稳定性同时被强烈激活。相对论电子主要通过冲浪机制在足部的 Buneman 不稳定性下快速产生。能谱具有超过上游离子动能的高能尾部，伴随着主要的热种群。这为在激波前缘的离子声波不稳定性提供了有利条件，这反过来又导致了额外的加速。大振幅离子 Weibel 不稳定性在足部产生电流片，这意味着在非常高的 M(A)区域的三维激波结构中通过磁重联存在另一种耗散机制。
