Interaction between a dust cloud and a magnetized plasma in relative motion

The interaction between a dust cloud and a magnetized plasma is investigated by use of an idealized model where the dust particles have uniform size, a uniform density within the dust cloud, and start with the same velocity across the magnetic field in the plasma´s rest frame. The interaction is found to be governed by a dimensionless parameter K which is a function of dust cloud, and ambient plasma, parameters. For K much smaller than unity, the interaction goes on for typically 1/(2πK) gyro times, with the particles in the dust cloud performing gyro motions with decreasing radius. For K close to unity, the dust motion is stopped on the order of a dust particle gyro time. For the case K≫1, the plasma in the flux tube through the dust cloud is dragged across the magnetic field over a distance of the order of Kr_d, where r_d is the dust gyro radius, before the motion is stopped. Some expected effects for a more realistic dust cloud with density gradients, and containing dust with a spread in size, are discussed. The results have bearing on dusty plasma in space, e.g., models of the formation of spokes in Saturn´s ring system