Kinetic Simulations of Cosmic-Ray-modified Shocks. I. Hydrodynamics
Kinetic Simulations of Cosmic-Ray-modified Shocks. I. Hydrodynamics
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DOI：
10.3847/1538-4357/abbe06
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发表时间：
2020-12-01
影响因子：
4.9
通讯作者：
Caprioli, Damiano
中科院分区：
文献类型：
--
作者：
Haggerty, Colby C.;Caprioli, Damiano
无碰撞等离子体激波是空间和天体物理系统中非热粒子加速的有效来源。我们使用混合(动能离子-流体电子)模拟来研究自生高能粒子(宇宙射线)对激波流体动力学的非线性反馈。当CR加速是有效的时，我们发现既有上游前兆的证据，其中流入的等离子体被压缩和加热，也有下游后游标的证据，其中CRS中的能量通量和放大的磁场发挥了动力学作用。第一次，我们评估了游标后的非线性磁涨落是如何以大约当地的阿尔芬速度相对于下游的等离子体优先远离激波的。磁能和CR能相对于热等离子体的漂移大大增加了相对于标准预测的激波压缩比，特别是在强激波时超过4。这样的修改对通过扩散激波加速而加速的粒子光谱也有影响，这一重要结果在一篇配套论文中进行了详细阐述。
Collisionless plasma shocks are efficient sources of nonthermal particle acceleration in space and astrophysical systems. We use hybrid (kinetic ion-fluid electron) simulations to examine the nonlinear feedback of the self-generated energetic particles (cosmic rays, CRs) on the shock hydrodynamics. When CR acceleration is efficient, we find evidence of both an upstream precursor, where the inflowing plasma is compressed and heated, and a downstream postcursor, where the energy flux in CRs and amplified magnetic fields play a dynamical role. For the first time, we assess how nonlinear magnetic fluctuations in the postcursor preferentially travel away from the shock at roughly the local Alfven speed with respect to the downstream plasma. The drift of both magnetic and CR energy with respect to the thermal plasma substantially increases the shock compression ratio with respect to the standard prediction, in particular exceeding 4 for strong shocks. Such modifications also have implications for the spectrum of the particles accelerated via diffusive shock acceleration, a significant result detailed in a companion paper.