WAVE GENERATION ASSOCIATED WITH DUST CLOUD EXPANSION INTO A PLASMA

Wave generation associated with the expansion of a dust cloud into a b ackground plasma across a magnetic field is studied by using numerical simulation and theoretical models. As the dust grains expand across t he magnetic held into the background plasma and charge up, an ambipola r electric held develops across the boundary layer between the negativ ely charged dust cloud and the background plasma. A strongly sheared e lectron E x B flow develops along the boundary. Plasma irregularities develop in response to the sheared electron flow velocity. It is noted that these irregularities are observed in the dust grain charge as we ll as the background plasma electron and ion densities. The fluctuatio ns in dust grain charge are interpreted to be a fundamental collective effect in the dusty plasma produced by the dust cloud expansion. A th eoretical model for the shear-driven instability in the dust cloud bou ndary is presented. In general the theoretical model predictions show good agreement with the numerical simulation results.