  The charging of conducting or alternatively insulating dust grains in a
supersonic plasma flow with a directed photon flux is studied by the
particle-in-cell method. The electron emission modifies the surface charge
distribution on a grain and in the surrounding plasma. The charge and potential
distributions on and around a dust grain are studied for different photon
fluxes and different angles of the incident unidirectional photons with respect
to the plasma flow velocity vector. Continuous and pulsed radiations are
considered. We show that photoemission allows controlling the charge on
conducting grains, and discuss the charging of stationary and spinning
insulating grains. Interactions between positively charged grains can be
stronger than for negatively charged grains. The simulations are carried out in
two spatial dimensions, treating ions and electrons as individual particles.
