On applicability of the fluid approach to the description of nonlinear processes in magnetoactive plasma

The paper discusses the difference between kinetic and hydrodynamic descriptions of nonlinear wave scattering and transformation in plasma with external magnetic fields. In particular, it gives a detailed study of electromagnetic wave scattering by fluctuations in a magnetoactive plasma. For the limiting case of cold plasmas, the results of the kinetic description are shown to reproduce the expressions obtained in the fluid approach. The applicability conditions of the latter are analyzed. The method of moments is applied to solve the kinetic equation and is thus shown to be efficient in the study of nonlinearity and thermal dispersion of fluctuations responsible for the wave scattering. The quantitative description of thermal effects can be provided only in terms of the kinetic approach