Modulational interaction of short-wavelength ion-acoustic oscillations in impurity-containing plasmas

The modulational interactions of ion acoustic waves are investigated for plasmas containing heavy impurity ions or dust particles. Low-frequency modulations arising from dust-acoustic oscillations are considered. It is found that instability of the short-wavelength ion-acoustic, or ion Langmuir, waves can develop for modulations with wavelengths larger as well as smaller than those of the pump waves. The latter possibility can result in the appearance of waves resonant with thermal ions. It follows that the bulk of the plasma ions can be heated. The corresponding one-dimensional ion Langmuir solitary waves are also discussed.