On the propagation and interaction of ultralow-frequency waves in a waveguide with gyrotropic plasma

Abstract

The propagation of ultralow-frequency (ULF) electromagnetic waves in a waveguide filled with magnetoactive plasma is consieered on the basis of the monoaxial crystal approximation which is more general than the MHD approximation. The formulas for the phase and group velocities of the ordinary (magnetoacoustic) and extraordinary waves (similar to Alfvén waves in the MHD approximation) are derived. It is shown that analysis outside the scope of the MHD approximation results in a finite (nonzero) velocity of energy propagation of the extraordinary wave (Alfvén wave at the limit) along the waveguide. The possible waveguide mode triplets satisfying the conditions of synchronism are found. Three-wave resonant parametric and nonlinear interaction between waves with such characteristics leads to effective spectral transformation of the ULF radiation.