Proton and electron fluxes on the surface of a dust grain in a plasma

Abstract

It is well known that the orbital motion limited approximation, being applied to dusty plasma, suggests that the electrons and ions of the plasma medium are independently absorbed by a dust grain. Moreover the classic version of the orbital motion limited approximation concedes that the interaction of the charged plasma particles with the dust is purely Coulomb, which means complete neglecting of the field screening phenomena. Such assumptions are only valid if the size of the dust particle is much smaller than the characteristic screening length, which in turn is much less than the mean free paths of electrons and ions in the plasma. In this case, application of the conservation laws of energy and angular omentum is enough to calculate the absorption cross section of electrons and ions by the dust particle. Herein an attempt is undertaken to treat the polarization of the dust particle itself in its interaction with the plasma particles, and it is demonstrated that the knowledge of the conservation laws of energy and angular momentum turns insufficient. It is shown that the absorption cross sections of electrons and ions of the plasma are determined by the condition that the kinetic energy of the incoming plasma particle should be equal to the maximum of the effective potential energy of their interaction with the dust grain. Ion and electron fluxes on the surface of a dust grain are calculated under the assumption that the corresponding velocity distributions are Maxwellian.