Electrodynamic properties of inhomogeneous magnetoactive plasma: low-frequency limit

Abstract

Low-frequency nonlinear electrodynamic properties of inhomogeneous magnetoactive plasmas are considered. Using the self-consistent field approximation, the nonlinear material relation between the polarization and the electric field strength in an inhomogeneous magnetoactive plasma is derived. In the case of a weak inhomogeneity of the plasma, the explicit expressions are derived for the linear susceptibility and the nonlinear susceptibilities for quasi-flute plasma motions with the thermal corrections taken into account. The nonlinear interaction of low-frequency oscillations in the inhomogeneous magnetized plasma results in a double cascade of waves in the wave-vector space (i.e., the decay, larger and smaller wave-vector magnitude as compared to that of the pump wave-vector). It is shown this property to be universal as a result of general energy and momentum conservation laws for the nonlinear interaction of waves in the weakly inhomogeneous plasma when the wave phase velocity is anisotropic. The conservation of the energy and the momentum under the nonlinear interaction is related to the symmetry properties of the nonlinear electric susceptibility. The double cascade usually is accompanied with the emergence of the structures in the plasma, strongly elongated in the direction perpendicular to the direction of the plasma inhomogeneity, and the formation of zonal particle flows in the same direction. Therefore the double cascade of waves may be considered as a self-organization process in the plasma. The low-frequency-fluctuation spectra are assumed to be formed under the nonlinear wave-wave interaction and the constant fluxes of nonlinear-interaction integrals corresponding to these spectra. A small-parameter expansion enables one to deduce a wave kinetic equation by regular means and to calculate the fluctuation for weakly turbulent plasma states on the bases of this equation. The stationary wave-intensity distribution are found for the plasma states with zero and non-zero fluxes of nonlinear-interaction integrals over the spectrum. There are considered: long-wave and short-wave convective oscillations, low-frequency drift waves, and electron convective waves. The nonlinear plasma motion in crossed magnetic and gravity fields is investigated. It is shown the phenomenon of a double interchange-wave cascade and the weak-interchange-turbulence spectra is determined. Finally, the nonlinear interaction of the magnetic electron waves is considered which accompanies with the nonlinear electron waves is of large-scale magnetic fields in plasma.