Ion acoustic waves in the presence of high frequency oscillators

Spatially varying high frequency oscillations will influence the electron motion in plasmas (through ponderomotive forces) and in turn affect the characteristics of ion acoustic oscillations. In this report we derive the dielectric function for long wavelength, low frequency ion acoustic waves in the presence of high frequency, short wavelength oscillations.

Apart from reproducing well known results this dielectric function shows the possibility of unstable ion acoustic waves for extreme intensities of high frequency oscillations. It is demonstrated that moderate intensities have a stabilizing effect on linearly unstable double humped ion distribution functions and it is argued that this effect may be of importance in laboratory experiments.

Finally we point out some generalisations.