Dynamics of ions during development of parametric instability of langmuir waves

Nonlinear regimes of one-dimensional parametric instabilities of long-wave plasma waves are considered for the cases when the average field energy density is less (Zakharov model) or greater (Silin model) than the plasma thermal energy. The process of generation of short-wave plasma waves and perturbations of ion density is found to be similar in both cases. It is shown that the ion energy after the instability is saturated proves to be of the order of the ratio of linear growth rate to the frequency in the case when the initial field energy exceeds the plasma thermal energy. In the opposite case of hot plasma, the ions acquire a part of initial field energy equal to the ratio of initial field energy to the plasma thermal energy. The trajectory crossing of ions in the vicinity of density cavities is a reason of instability quenching in both cases.