Adiabatic evolution of phase space electron-hole in plasmas with super-thermal electrons

The possibility of the nonlinear decay of a localized perturbation into the ion-acoustic solitons is studied. This corresponds to the formation of several electrons-holes in the phase space. The plasma is assumed to contain a population of super-thermal electrons and therefore the kappa distribution is used to model the high energy tail in the electron distribution function. The formalism is derived near the ion plasma frequency. In this range of frequency, the ion dynamics is considerable and the ion-acoustic solitons are the stationary solutions of the governing equations. It is shown that a slowly varying dynamics of the order of ion motions causes an initial Gaussian hole to be disintegrated into a number of electron-holes. The non-stationary process of the hole formation is adiabatic. The hole velocities, which are of the order of the ion-acoustic velocity, are slightly different. The set of ion-acoustic solitons forms neighboring (neighboring in phase space) holes. The influence of both trapped and super-thermal electrons on this process is studied.