A Study of Ion Drag for Ground and Microgravity Dusty Plasma Experiments

This paper presents the results of a recent study of the interaction between charged dust particles and plasma ions through the electrostatic and ion drag forces in a dc glow discharge plasma. Measurements of the dust particles motion are carried out using particle image velocimetry (PIV). When an electrostatic perturbation is applied to the dust cloud, the particle motion, in response to the perturbation, is shown to reverse direction as the gas pressure is increased. An analysis of the dust particle motion and background plasma parameters suggests that there is a change in the equilibrium position and competition between the electrostatic force and the ion drag force on the particles that lead to the asymmetric motion of the cloud. The ion drag and electric forces on the dust particles are calculated at each pressure using detailed measurements of the plasma parameters, as measured by a single Langmuir probe. The analysis of these measurements suggests that the reversal of direction is a result of the change in the electric field in the plasma, but that the effectiveness of the perturbation at displacing the dust cloud is controlled by the ion drag force.