Effects of beat-wave electron trapping on stimulated Raman and Thomson scattering

The influence of electron trapping on a large amplitude plasma oscillation driven by the nonlinear interaction of two electromagnetic waves (stimulated Raman scattering) is studied analytically and by means of numerical simulation. When the plasma oscillation is resonantly excited to sufficiently large amplitude and electron trapping occurs, there ensues considerable modification of the electron velocity distribution function. The stimulated scattering ceases to be a resonant three-wave process but continues as induced scattering by resonant electrons (stimulated Thomson scattering). The scattering of the electromagnetic waves becomes slower, but does not terminate with the onset of particle trapping in the beat wave.