Simulations of relativistic collisionless shocks: shock structure and particle acceleration
Simulations of relativistic collisionless shocks: shock structure and particle acceleration
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相对论无碰撞冲击的模拟：冲击结构和粒子加速度
DOI：
10.1063/1.2141897
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发表时间：
2005
期刊：
影响因子：
--
通讯作者：
A. Spitkovsky
中科院分区：
文献类型：
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作者：
A. Spitkovsky
本文讨论了电子-正电子对等离子体中相对论性无碰撞冲击的三维模拟。激波结构主要由激波的磁化强度（“sigma”参数）控制。我们演示了激波的结构如何作为垂直激波的函数而变化。在低磁化强度下，激波主要由维贝尔不稳定性介导，产生超过初始磁场的瞬态磁场。在较大的磁化强度下，激波以磁反射为主。我们证明了过渡发生的位置，并认为在自然界中（在多个空间维度中）不可能有非常低磁化强度的无碰撞冲击。我们进一步讨论了这些激波的加速特性，并表明高磁化强度的垂直激波在三维中不能有效地加速非热粒子。在其他天体物理学应用中，这可能对伽马射线暴和脉冲星风流出的结构和组成构成限制。
We discuss 3D simulations of relativistic collisionless shocks in electron-positron pair plasmas using the particle-in-cell (PIC) method. The shock structure is mainly controlled by the shock's magnetization (''sigma'' parameter). We demonstrate how the structure of the shock varies as a function of sigma for perpendicular shocks. At low magnetizations the shock is mediated mainly by the Weibel instability which generates transient magnetic fields that can exceed the initial field. At larger magnetizations the shock is dominated by magnetic reflections. We demonstrate where the transition occurs and argue that it is impossible to have very low magnetization collisionless shocks in nature (in more than one spatial dimension). We further discuss the acceleration properties of these shocks, and show that higher magnetization perpendicular shocks do not efficiently accelerate nonthermal particles in 3D. Among other astrophysical applications, this may pose a restriction on the structure and composition of gamma-ray bursts and pulsar wind outflows.