A MODEL EQUATION FOR NONRESONANT INTERACTING ION-ACOUSTIC PLASMA-WAVES

The interaction among non-resonant ion acoustic plasma waves with diff erent group velocities that are not close to each other is studied by an asymptotic perturbation method, based on Fourier expansion and spat io-temporal rescaling. It is shown that the nonlinear Schrodinger equa tion is not adequate, and instead a model system of nonlinear evolutio n equations is necessary to describe oscillation amplitudes of Fourier modes. This system is C-integrable, i.e. it can be linearized through an appropriate transformation of the dependent and independent variab les. We demonstrate that the subclass of localized solutions gives ris e to a solitonic phenomenology. These solutions propagate with the rel ative group velocity and maintain their shape during a collision, the only change being a phase shift. Numerical calculations confirm the va lidity of these predictions.