Suppression and Enhancement of an Ion-Sound Instability by Nonlinear Resonance Effects in a Plasma

Results are presented which show the classical anharmonic resonance effects (including hysteresis) on a marginal ion sound instability, when forcing at the fundamental and the subharmonic frequencies. Also, when the instability is well defined it appears to be-have as a classical Van der Pol oscillator for drive frequencies near the fundamental and the subharmonics.