Interaction of two elongated dust grains in flowing plasmas studied by numerical simulations

Interaction potentials between two insulating elongated dust grains in a supersonic plasma flow are studied by a particle-in-cell numerical method. It is found that the spatial variations of the charge distribution and the plasma potential depend on the orientation and the relative distance of the dust grains. For the case of two grains aligned perpendicular to the flow, a single wake and region of enhanced ion density are observed for small relative distances. The ion flux can be enhanced between such grains. For grains aligned parallel to the flow, the resulting wake is not a linear combination of the wakes behind a single grain, and the grain charge and interaction potentials strongly depend on their relative orientations. The simulations are carried out in two spatial dimensions, treating ions and electrons as individual particles. The case of two spherical grains, with separation vector perpendicular to the plasma flow direction, is considered for comparison.