Modulational instability in the beat-wave generation

Abstract

The coupling of a large amplitude plasmon, generated by the beat-wave process, to ion acoustic waves may lead to modulational or decay instabilities, which are investigated here. A general dispersion relation obtainable from Zakharov equations predicts large growth rates (∼ω_pi) for short wavelength modulations. To avoid these, extremely short pulse lengths are required in the beat-wave experiments. Due to the very long wavelength of the beat-plasmon, the decay instability is not likely below the ke V-temperatures.