Collisionless shocks and turbulence in nonthermal sources of radiation

我们研究了壳型超新星遗迹(SNR)正激波附近的磁湍动特性及其对高能粒子加速的作用。彻底了解湍流和高能粒子之间的关系将对一些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。由于无碰撞激波作用下的等离子体湍流具有很小的波长尺度，不能用MHD方法真实地描述，所以我们进行动力学粒子在单元(PIC)中的模拟。我们的并行代码是高度可扩展的，因此允许在适当的广泛物理范围内进行计算机实验。我们的研究是由以下基本问题驱动的：在具有有效粒子加速的无碰撞激波附近，强磁湍流的特征是什么？另外，强湍流介质中无碰撞激波的特性是什么？虽然已经对相对论碰撞的等离子体壳层及其相关激波进行了长期演化研究，但最重要的是研究我们对其有更直接的观测，并知道其几何结构的系统：SNR的非相对论激波。

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.