FLUID MODELS FOR KINETIC EFFECTS ON COHERENT NONLINEAR ALFVEN WAVES .2. NUMERICAL-SOLUTIONS

The influence of various kinetic effects (e.g., Landau damping, diffus ive and collisional dissipation, and finite Larmor radius terms) on th e nonlinear evolution of finite amplitude Alfvenic wave trains in a fi nite-beta environment is systematically investigated using a novel, ki netic nonlinear Schrodinger (KNLS) equation. The dynamics of Alfven wa ves is sensitive to the sense of polarization as well as the angle of propagation with respect to the ambient magnetic field. Numerical solu tion for the case with Landau damping reveals the formation of dissipa tive structures, which are quasi-stationary, S-polarized directional ( and rotational) discontinuities which self-organize from parallel prop agating, linearly polarized waves. Parallel propagating circularly pol arized packets evolve to a few circularly polarized Alfven harmonics o n large scales. Stationary are-polarized rotational discontinuities fo rm from obliquely propagating waves. Collisional dissipation, even if weak, introduces enhanced wave damping when beta is very close to unit y. Cyclotron motion effects on resonant particle interactions introduc e cyclotron resonance into the nonlinear Alfven wave dynamics. (C) 199 7 American Institute of Physics.