Nonlinear stimulated Brillouin scattering in inhomogeneous plasmas

Abstract

The combined effects of ion-acoustic nonlinearity and plasma inhomogeneity on a stimulated Brillouin scattering (SBS) are considered in the model of coupled Korteweg–de Vries (KdV) and electromagnetic wave equations. In the regime of linear ion-acoustic waves the results are in good agreement with the existing linear theories of SBS and demonstrate the regimes of both convective and absolute instabilities. New features of SBS saturation due to ion-acoustic nonlinearity and pump depletion in inhomogeneous plasmas are found. They include the scaling for saturated reflectivity, the transition from convective to absolute growth, and the temporal pulsations of the reflectivity coefficient. The autoresonance process is analyzed and its relevance to SBS for realistic plasma parameters is discussed.