Particle Acceleration by Magnetohydrodynamic Turbulence
Particle Acceleration by Magnetohydrodynamic Turbulence
复制标题
磁流体动力湍流的粒子加速
DOI：
10.1086/498967
复制
发表时间：
2005
期刊：
影响因子：
--
通讯作者：
A. Lazarian
中科院分区：
文献类型：
--
作者：
Jungyeon Cho;A. Lazarian
对 MHD 湍流理解的最新进展需要对粒子加速的图像进行修改。我们利用最近在强和弱 MHD 湍流中建立的慢速和快速 MHD 模式的缩放，对磁压主导（低 β）和气态压力主导（高 β）等离子体中的粒子加速进行系统研究。我们在慢速和快速粒子扩散极限下考虑大规模压缩的加速。我们将结果与共振散射和传输时间阻尼 (TTD) 产生的加速度进行比较。我们确定快速模式比慢速模式更有效地加速粒子。我们发现，当空间扩散率较小时，通过俯仰角散射和 TTD 进行的粒子加速在慢速或快速模式的加速中占主导地位。当粒子的空间扩散速率较高时，我们在弱湍流中通过慢速和快速模式建立了粒子加速效率的增强。我们证明，高超音速湍流是粒子加速的有效媒介。我们发现，即使是不可压缩的湍流也可以在与粒子平均自由程相当的尺度上加速粒子。
Recent advances in understanding of MHD turbulence call for revisions in the picture of particle acceleration. We make use of the recently established scaling of slow and fast MHD modes in strong and weak MHD turbulence to provide a systematic study of particle acceleration in magnetic pressure-dominated (low β) and gaseous pressure-dominated (high β) plasmas. We consider the acceleration by large-scale compressions in both slow and fast particle diffusion limits. We compare the results with the acceleration rate that arises from resonance scattering and transit-time damping (TTD). We establish that fast modes accelerate particles more efficiently than slow modes. We find that particle acceleration by pitch-angle scattering and TTD dominates acceleration by slow or fast modes when the spatial diffusion rate is small. When the rate of spatial diffusion of particles is high, we establish an enhancement of the efficiency of particle acceleration by slow and fast modes in weak turbulence. We show that highly supersonic turbulence is an efficient agent for particle acceleration. We find that even incompressible turbulence can accelerate particles on the scales comparable with the particle mean free path.