Fluid Models for Kinetic Effects on Coherent Nonlinear Alfven Waves. II. Numerical Solutions

摘要

The influence of various kinetic effects (e.g. Landau damping, diffusive andcollisional dissipation, and finite Larmor radius terms) on the nonlinearevolution of finite amplitude Alfvenic wave trains in a finite-beta environmentis systematically investigated using a novel, kinetic nonlinear Schrodinger(KNLS) equation. The dynamics of Alfven waves is sensitive to the sense ofpolarization as well as the angle of propagation with respect to the ambientmagnetic field. Numerical solution for the case with Landau damping reveals theformation of dissipative structures, which are quasi-stationary, S-polarizeddirectional (and rotational) discontinuities which self-organize from parallelpropagating, linearly polarized waves. Parallel propagating circularlypolarized packets evolve to a few circularly polarized Alfven harmonics onlarge scales. Stationary arc-polarized rotational discontinuities form fromobliquely propagating waves. Collisional dissipation, even if weak, introducesenhanced wave damping when beta is very close to unity. Cyclotron motioneffects on resonant particle interactions introduce cyclotron resonance intothe nonlinear Alfven wave dynamics.