Parametric Excitations of Ion Plasma Oscillations

Parametric excitations of ion plasma oscillations are investigated by using a simple model based on the modulation of ion density in the uniform electron background. This model is useful to calculate the higher order nonlinear terms, and gives a good interpretation to the new nonlinear phenomena observed in a mercury vapour plasma without magnetic field. The nonlinear effects observed are; (1) the frequency shift and the amplitude increase of the resonant oscillations with increasing of pumping power, (2) the existence of the resonance frequency region, and (3) the asymmetrical parametric excitation with hysteresis.