Bernstein mode aided anomalous absorption of laser in a plasma

Abstract

A laser propagating through a plasma, in the presence of an electron Bernstein wave, undergoes nonlinear mode coupling, producing a beat mode (ω+ω0, k+k0) where (ω0, k0) and (ω, k) are the frequency and wave number of the laser and the Bernstein mode. The oscillatory electron velocity associated with this beat mode couples with electron density perturbation due to the Bernstein wave to produce a nonlinear current at the laser frequency. When the beat mode is Landau damped on electrons, the nonlinear current at the laser frequency has an in-phase component with the laser field, giving rise to anomalous resistivity. The normalized anomalous resistivity is found to be maximum for q=∣k+k0∣νth∕(ω+ω0)≈0.8–0.9.