New mechanisms of resonant absorption of electromagnetic waves in a magnetized plasma

Absorption of electromagnetic waves in a magnetized plasmas is investigated in a tremendous number of papers. No account has been taken however of the influence of a strong quasistationary electric field. By a strong electric field one means the case, when the electric drift velocity is comparable with the particle velocity /λ-3/. It corresponds to the magnetohydrodynamic (MHD) approximation. In this approximation dynamics of the charged-particle in a resonant high-frequency wave packets is considered. Weak relativistic effects are taken into account. It is shown that a strong electric field can alter substantially the character of the resonant wave-particle interaction and the mechanism of energy exchange between them. In particular one can see that the presence of a strong electric quasistationary field makes it possible for a particle to experience Cerenkov resonance in a transverse electromagnetic wave, propagating along an external magnetic field. It is in principle not realizable in a weak electric field. As an example, the nonlinear damping rate of the whistler is calculated for Cerenkov resonance and it is shown that it can be comparable with the damping rate in cyclotron-resonance interaction between a wave and a particle. In the case of a longitudinal wave propagating along a magnetic field cyclotron-resonance interaction can take place, something impossible in principal in a weak electric field