Particle acceleration by magnetohydrodynamic turbulence

被引:64
作者
Cho, JY [1 ]
Lazarian, A
机构
[1] Chungnam Natl Univ, Dept Astron & Space Sci, Taejon, South Korea
[2] Univ Wisconsin, Dept Astron, Madison, WI 53706 USA
基金
美国国家科学基金会;
关键词
acceleration of particles; MHD; turbulence;
D O I
10.1086/498967
中图分类号
P1 [天文学];
学科分类号
0704 ;
摘要
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 beta) and gaseous pressure dominated (high beta) 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.
引用
收藏
页码:811 / 826
页数:16
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