Effect of dust-charge variation on ion-wave decay interaction in dusty plasma

Three-wave decay interaction of electrostatic ion acoustic waves in a plasma with variable-charge dust grains is reconsidered. The evolution equations describing the decay interaction are obtained and the decay of an ion acoustic wave into another ion acoustic wave and a dust acoustic wave is investigated in detail. It is confirmed that the decay wave must be backward propagating, even if strong charge relaxation and the short wavelength regime are included. However, in both cases, the decay instability can be weakened or suppressed.