Electron Bernstein wave excitation by counterpropagating electromagnetic waves in a plasma

Abstract

Two high-power counterpropagating electromagnetic waves (ω1,k1x̂) and (ω2,−k2x̂) in a low-density plasma in the presence of a static magnetic field Bsẑ, drive an electron Bernstein wave at the beat frequency ω=ω1−ω2 and k=(k1+k2)x̂, when ω∼ωc⪡ω1,ω2 and kρ≥1, where ωc is the electron cyclotron frequency and ρ is the Larmor radius. The electromagnetic waves exert a ponderomotive force on the electrons and resonantly drive the Bernstein mode(ω,k). When the pump waves have finite z extent, the Bernstein wave has an effective kz and a component of group velocity in the direction of the magnetic field, leaking it out of the interaction region, limiting the level of the Bernstein mode. Plasma inhomogeneity also introduces convection losses. However, the electron Bernstein mode potential could still be significantly greater than the ponderomotive potential.