Electron acceleration in laboratory-produced turbulent collisionless shocks
Electron acceleration in laboratory-produced turbulent collisionless shocks
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DOI：
10.1038/s41567-020-0919-4
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发表时间：
2020-06-08
期刊：
影响因子：
19.6
通讯作者：
Park, H-S
中科院分区：
文献类型：
--
作者：
Fiuza, F.;Swadling, G. F.;Park, H-S
天体物理学上的无碰撞冲击是宇宙中最强大的粒子加速器之一。由超音速等离子体流与星际介质的剧烈相互作用产生的超新星遗迹激波被观测到可以放大磁场（1）并将电子和质子加速到高度相对论速度（2-4）。在已经建立的扩散激波加速模型（5）中，相对论性粒子被重复的激波交叉加速。然而，这需要一个单独的机制，预加速粒子，使激波穿越。这就是所谓的“注入问题”，它与电子特别相关，并且仍然是冲击加速中最重要的难题之一（6）。在大多数天体物理学冲击中，冲击结构的细节无法直接解析，这使得识别注入机制具有挑战性。在这里，我们报告的结果，从激光驱动的等离子体流实验，和相关的模拟，探测年轻超新星遗迹相关的条件下形成的湍流碰撞冲击。我们表明，电子可以有效地加速在一阶费米过程中产生的冲击过渡到相对论非热能的小尺度湍流，帮助克服注入问题。我们的观察提供了新的见解，电子注入冲击和打开的方式，控制实验室研究的物理基础宇宙accelerator.In激光等离子体实验补充模拟，电子加速湍流碰撞冲击观察。这项工作澄清了预加速到相对论能量所需的扩散冲击加速的发病。
Astrophysical collisionless shocks are among the most powerful particle accelerators in the Universe. Generated by violent interactions of supersonic plasma flows with the interstellar medium, supernova remnant shocks are observed to amplify magnetic fields(1) and accelerate electrons and protons to highly relativistic speeds(2-4). In the well-established model of diffusive shock acceleration(5), relativistic particles are accelerated by repeated shock crossings. However, this requires a separate mechanism that pre-accelerates particles to enable shock crossing. This is known as the 'injection problem', which is particularly relevant for electrons, and remains one of the most important puzzles in shock acceleration(6). In most astrophysical shocks, the details of the shock structure cannot be directly resolved, making it challenging to identify the injection mechanism. Here we report results from laser-driven plasma flow experiments, and related simulations, that probe the formation of turbulent collisionless shocks in conditions relevant to young supernova remnants. We show that electrons can be effectively accelerated in a first-order Fermi process by small-scale turbulence produced within the shock transition to relativistic non-thermal energies, helping overcome the injection problem. Our observations provide new insight into electron injection at shocks and open the way for controlled laboratory studies of the physics underlying cosmic accelerators.In laser-plasma experiments complemented by simulations, electron acceleration is observed in turbulent collisionless shocks. This work clarifies the pre-acceleration to relativistic energies required for the onset of diffusive shock acceleration.