Raman Side-Scatter Instability in Nonuniform Plasma

Abstract

For the Raman instability in nonuniform plasma, the linear space-time asymptotic response consists of two parts, convectively growing wave packets and temporally growing localized side-scattered eigenmodes. Eigenmodes dominate the response only after the growth of the side-scattered wave packets is terminated by refraction from their resonance zones. A finite pump-beam diameter typically ends all growth before eigenmodes appear, except near quarter-critical density. These considerations may reconcile simulations, previous theories, and experiments.