40 20 49 v 1 9 F eb 2 00 4 Oblique amplitude modulation of dust - acoustic plasma waves ∗

Theoretical and numerical studies are presented of the nonlinear amplitude modulation of dustacoustic (DA) waves propagating in an unmagnetized three component, weakly-coupled, fully ionized plasma consisting of electrons, positive ions and charged dust particles, considering perturbations oblique to the carrier wave propagation direction. The stability analysis, based on a nonlinear Schrödinger-type equation (NLSE), shows that the wave may become unstable; the stability criteria depend on the angle θ between the modulation and propagation directions. Explicit expressions for the instability rate and threshold have been obtained in terms of the dispersion laws of the system. The possibility and conditions for the existence of different types of localized excitations have also been discussed.