Stimulated Brillouin side-scattering of the beat wave excited by two counter-propagating X-mode lasers in magnetized plasma

Abstract

The stimulated Brillouin scattering (SBS) of nonresonant beat mode in the presence of static magnetic field is investigated in a plasma. Two counter-propagating lasers of frequencies (ω1 and ω2) and wave vectors (k1 and k2) drive a nonresonant space charge beat mode at the phase matching condition of frequency ω0≈ω1∼ω2 and wave number k→0≈k→1+k→2. The driver wave parametrically excites a pair of ion acoustic wave (ω,k→) and a sideband electromagnetic wave (ω3,k→3). The beat wave couples with the sideband electromagnetic wave to exert a nonlinear ponderomotive force at the frequency of ion acoustic wave. Density perturbations due to ion acoustic wave and ponderomotive force couple with the oscillatory motion of plasma electron due to velocity of beat wave to give rise to a nonlinear current (by feedback mechanism) responsible for the growth of sideband wave at resonance. The growth rate of SBS was reduced (from ∼1012s−1 to 1010s−1) by applying a transverse static magnetic field ∼90 T. The present study can be useful for the excitation of fast plasma waves (for the purpose of electron acceleration) by two counter-propagating laser beams.