White-light parametric instabilities in plasmas

Abstract

Parametric instabilities driven by partially coherent radiation in plasmas are described by a generalized statistical Wigner-Moyal set of equations, formally equivalent to the full wave equation, coupled to the plasma fluid equations. A generalized dispersion relation for Stimulated Raman Scattering driven by a partially coherent pump field is derived, revealing a growth rate dependence, with the coherence width $σ$ of the radiation field, scaling with $1/σ$ for backscattering (three-wave process), and with $1/σ^{1/2}$ for direct forward scattering (four-wave process). Our results demonstrate the possibility to control the growth rates of these instabilities by properly using broadband pump radiation fields.

6 pages, 3 figures, accepted for publication in Phys. Rev. Lett