Collisionless shocks and turbulence in nonthermal sources of radiation

本文探讨了壳型超新星遗迹（SNR）前激波附近磁湍流的性质及其在高能粒子加速中的作用。彻底理解湍流和高能粒子之间的关系将对许多重要的科学问题产生深远的影响，其中包括宇宙射线的起源，原始磁场的产生，以及远离平衡的系统中驱动湍流的性质。由于无碰撞冲击下的等离子体湍流具有非常小的波长尺度，无法用MHD方法真实地描述，因此我们进行了动能粒子池（PIC）模拟。我们的并行代码是高度可扩展的，因此允许在适当范围的物理尺度上进行计算机实验。我们的研究是由以下几个基本问题驱动的：无碰撞冲击附近的强磁湍流具有有效粒子加速度的特征是什么？此外，强湍流介质中无碰撞冲击的性质是什么？虽然长期演化研究已经对相对论性碰撞等离子体壳和相关激波进行了研究，但研究我们有更多直接观测的系统，以及我们知道几何形状的系统：信噪比的非相对论性激波，是至关重要的。

We explore the properties of magnetic turbulence near the forward shocks of shell-type supernova remnants (SNR) and their role the acceleration of energetic particles. A thorough understanding of the relations between turbulence and energetic particles would have profound consequences for a number of important scientific questions, among them the origin of cosmic rays, the generation of primordial magnetic fields, and the properties of driven turbulence in a system far from equilibrium. We perform kinetic Particle-in-Cell (PIC) simulations, because plasma turbulence at collisionless shocks has very small wavelength scales and cannot be realistically described with MHD methods. Our parallel code is highly scalable and thus permits computer experiments over an appropriately wide range of physical scales.Our research is driven by the following basic questions: What are the characteristics of strong magnetic turbulence near a collisionless shock with efficient particle acceleration? Also, what are the properties of collisionless shocks in a strongly turbulent medium? While longterm-evolution studies have been performed for relativistically colliding plasma shells and the associated shocks, it is of utmost importance to study the systems for which we have much more direct observations, and for which we know the geometry: the nonrelativistic shocks of SNRs.