Alfven - wave particle interaction in finite-dimensional self-consistent field model

A low-dimensional Hamiltonian model is derived for the acceleration of ions in finite-amplitude Alfven waves in a finite-pressure plasma sheet. The reduced low-dimensional wave - particle Hamiltonian is useful for describing the reaction of the accelerated ions on the wave amplitudes and phases through the self-consistent fields within the envelope approximation. As an example, we show that for a single Alfven wave in the central plasma sheet of the Earth close-quote s geotail, modeled by the linear pinch geometry called the Harris sheet, the time variation of the wave amplitude during the acceleration of fast protons. copyright 1999 American Institute of Physics