Model simulations of Langmuir wave turbulence induced by the Raman instability

Abstract

One and two dimensional simulations of a variant of Zakhavov’s equations of nonlinear Langmuir wave dynamics, driven by a model source owing to Stimulated Raman backscatter (SRS) at wavenumber k1, yield constitutive relations between the energy injection rate, 〈ε〉, from SRS, and various local Langmuir wave turbulence properties, such as the mean spatial and spectral energy densities and effective damping rate, νeff. In the inertial regime, where the Langmuir wave damping is significant only for k>k1, it is found that these relations are insensitive to the source bandwidth, ν, if ν⩾νeff, and are well represented by power laws in 〈ε〉. Approximate scaling relations of νeff with the ion acoustic damping rate coefficient, νia, show that the turbulence is over-stable with respect to the Langmuir decay instability, as determined by νia and νeff, by a factor of order unity.