EXCITATION OF NONLINEAR ALFVEN WAVES BY AN ION-BEAM IN A PLASMA .1. RIGHT-HAND POLARIZED WAVES

A self-consistent theory of MHD wave excitation in the solar wind plas ma by a cold ion beam moving along the ambient magnetic field is devel oped. Using analytical and numerical technics, we investigate the line ar stage of the exponential growth of wave amplitudes, their saturatio n due to trapping or pitch angle diffusion of resonant ions and the st eepening of the wave profile due to plasma nonlinearity. The derivativ e nonlinear Schrodinger equation was used to describe the nonlinear in put of plasma particles, and a hybrid method of incomplete numerical s imulation was used to investigate strongly nonlinear motion of resonan t particles. We have studied the temporal behavior of wave energy for waves propagating in both positive and negative directions in relation to the magnetic field, directions and we have found that in cases und er consideration the steepening profile developed only for right-hand polarized waves. The physical mechanism for wave steepening is higher harmonic generation due to plasma nonlinearity.