Charging of Dust in the Presence of a Directed Photon Flux: Numerical Simulations

The charging of conducting and insulating dust grains in flowing plasmas in the presence of a directed photon flux is studied using Particle-In-Cell numerical simulations. We analyze the charge on dust grains for different photon fluxes and different angles of the photon incidence with respect to the supersonic plasma flow direction. For conducting grains we find that the total charge can be effectively controlled by the photon flux. On insulating grains, an electric dipole moment associated with the photoemission develops. A positive dust charge and photoelectrons distort several of the properties of the plasma surrounding the dust particle, and electrons are no longer Boltzmann distributed locally. Our results are compared with the case obtained without photoemission. The analysis is carried out in two spatial dimensions, with electrons and ions treated as individual particles.