The effect of dust grain size on the floating potential of dust in a collisionless plasma

Dust immersed in plasma quickly charges to a potential where the ion and electron currents to it balance; this is the floating potential. In order to determine dust behaviour the floating potential must be known. The most used theory for determining this is orbital motion limited (OML). The OML floating potential depends on the ion to electron temperature ratio (beta) and the plasma ion species (A). In reality the floating potential also depends strongly on the size of the dust grain (rho = a/lambda(D), where a is the radius of the grain and lambda(D) is the Debye length). Using a particle-in-cell code, dust is simulated in a collisionless plasma, the floating potential is investigated and the expressions provided allowing fast and accurate prediction of the floating potential as a function of beta, A and rho.