Dust in the Ion Wind: A Model for Plasma Dust Particle Dynamics

A model is developed for the forces acting on a micrometer-size particle (dust) suspended within a plasma sheath. The significant forces acting on a single particle are gravity, neutral gas drag, electric field, and the ion wind due to ion flow to the electrode. It is shown that an instability in the small-amplitude dust oscillation might exist if the conditions are appropriate. In such a case the forcing term due to the ion wind exceeds the damping of the gas drag. The basic physical cause for the instability is that the ion wind force can be a decreasing function of the relative ion-particle velocity. However it seems very unlikely the appropriate conditions for instability are present in typical dusty plasmas