A Method for Nonlinear Plasma Wave Kinetics

Abstract

A new method is presented to investigate the nonlinear wave kinetics in a plasma. While most previous theories assume that the wave-amplitudes and other average quantities vary very little within the duration time τ of the wave-wave interaction, the present theory is valid under much less restrictive condition that their variation is small in the oscillation periods of the waves under consideration. The method consists in a systematic use of the interaction representation; the unique point of the present method lies in the introduction of many time variables in order to describe phenomena with many physical quantities in a simple manner. The method is applied to the investigation of quasi-linear and weakly turbulent evolution of the system. Several new features, including the amplitude oscillation discussed in a previous report, are derived for the case where the characteristic timescale of the wave amplitude is short compared with τ.