Charging and dynamics of a dust grain in the wake of another grain in flowing plasmas

The charging of a dust grain in supersonic plasma flows in the wake of another grain is studied by numerical simulations. While entering the Mach cone originating from the upstream grain, the grain is discharged by scattered ions. Electrostatic forces acting on the grain in the wake will move it to the stable position in the wake at a distance close to the electron Debye length from the upstream grain. The onset for discharging can be used to estimate the ion flow speed in the system. The simulations are carried out with the DiP3D code, a three-dimensional particle-in-cell code where both electrons and ions are represented as numerical particles [W. J. Miloch et al., Nonlinear Processes Geophys. 14, 575 (2007); New J. Phys. 11, 043005 (2009)]. (C) 2010 American Institute of Physics. [doi:10.1063/1.3488252]