Stochastic charge fluctuations in dusty plasmas

We consider the stochastic properties of charge fluctuations of noninteracting particles surrounded by a stationary, undisturbed plasma of electrons and singly charge positive ions. For unscreened Coulomb interaction in the orbit-motion limit the mean particle charge and the variance of the fluctuations are proportional to the particle size. The result applies to both Maxwellian and non-Maxwellian electrons as well as to charging by ion winds. When the polarizability of the particle is included in the electrostatic interaction, both the ion and electron currents to the particle increase and the mean particle charge becomes more negative. Except for particles in the low nanometer range, the effect of the polarizability can be neglected at the electron temperatures encountered in typical plasmas.