论文标题
完全动力学等离子体湍流中的离子和电子加速度
Ion and Electron Acceleration in Fully Kinetic Plasma Turbulence
论文作者
论文摘要
通常调用湍流来解释空间和天体物理等离子体中非热颗粒的起源。通过3D完全动力学的细胞模拟，我们证明了低$β$等离子体中的湍流（$β$是等离子体压力与磁压的比率）将离子和电子加速到具有幂律能量范围的非热能分布。离子光谱比电子频谱更难，并且两种分布的较高$β$都更加陡峭。我们表明，电子的能量伴随着明显的能量依赖性俯仰角各向异性，大多数电子平行于局部磁场移动，而离子则大致保持各向同性。我们证明，来自热池的颗粒注入发生在高电流密度的区域。与磁重新连接相关的平行电场负责电子的初始能量增益，而垂直电场控制离子的整体能量。我们的发现对非热颗粒在空间和天体物理等离子体中的起源具有重要意义。
Turbulence is often invoked to explain the origin of nonthermal particles in space and astrophysical plasmas. By means of 3D fully kinetic particle-in-cell simulations, we demonstrate that turbulence in low-$β$ plasmas ($β$ is the ratio of plasma pressure to magnetic pressure) accelerates ions and electrons into a nonthermal energy distribution with a power-law energy range. The ion spectrum is harder than the electron one, and both distributions get steeper for higher $β$. We show that the energization of electrons is accompanied by a significant energy-dependent pitch-angle anisotropy, with most electrons moving parallel to the local magnetic field, while ions stay roughly isotropic. We demonstrate that particle injection from the thermal pool occurs in regions of high current density. Parallel electric fields associated with magnetic reconnection are responsible for the initial energy gain of electrons, whereas perpendicular electric fields control the overall energization of ions. Our findings have important implications for the origin of nonthermal particles in space and astrophysical plasmas.
