Quasi-linear theory of cosmic ray transport and acceleration: The role of oblique magnetohydrodynamic waves and transit-time damping

被引:146
作者
Schlickeiser, R
Miller, JA
机构
[1] Max Planck Inst Radioastron, D-53010 Bonn, Germany
[2] Univ Alabama, Dept Phys, Huntsville, AL 35899 USA
关键词
acceleration of particles; cosmic rays; diffusion; magnetic fields; plasmas; Sun; particle emission;
D O I
10.1086/305023
中图分类号
P1 [天文学];
学科分类号
0704 ;
摘要
We calculate quasi-linear transport and acceleration parameters for cosmic ray particles interacting resonantly with undamped fast-mode waves propagating in a low-beta plasma. For super-Alfvenic particles and a vanishing cross-helicity state of the fast-mode waves, we demonstrate that the rate of adiabatic deceleration vanishes, and that the momentum and spatial diffusion coefficients can be calculated from the Fokker-Planck coefficient D-mu mu. Adopting isotropic fast-mode turbulence with a Kolmogorov-like turbulence spectrum, we demonstrate that D-mu mu is the sum of contributions from transit-time damping and gyroresonant interactions. Gyroresonance refers to \n\not equal 0 resonant particle-wave interactions. Transit-time damping refers to the n=0 interaction of particles with the compressive magnetic field component of the fast-mode waves. We show that transit-time damping provides the dominant contribution to pitch-angle scattering in the interval epsilon less than or equal to\mu\less than or equal to 1, where epsilon is the ratio of Alfven to particle speed. In the interval \mu\<epsilon, transit-time damping does not occur, and gyroresonance provides a small but finite contribution to particle scattering. As a consequence, the momentum diffusion coefficient is mainly determined by the transit-time damping contribution. On the other hand, since the spatial diffusion coefficient and the related mean free path are given by the average over mu of the inverse of D-mu mu), these spatial transport parameters are determined by the contribution from the interval \mu\<epsilon. Pie also calculate the cosmic ray transport parameters for plasma turbulence consisting of a mixture of isotropic fast-mode waves and slab Alfven waves. Here, the momentum diffusion coefficient is determined by the transit-time damping of the fast-mode waves, and is a factor 1n epsilon(-1) larger than in the case of pure slab Alfven wave turbulence. The mean free path and the spatial diffusion coefficient are modified significantly from the pure fast-mode case, since the crucial scattering at \mu\<epsilon is now provided by gyroresonances with slab Alfven waves. The mean free path is a constant at nonrelativistic energies, and may account for the legendary lambda(fit)-lambda(QLT) discrepancy of sellar energetic particles.
引用
收藏
页码:352 / 378
页数:27
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