Simulation of electrorheological plasmas with superthermal ion drift

Abstract

By applying an external electric AC field to a dusty plasma, the micro-particles arrange in strings or chains caused by the wake potential between the micro-particles due to the ion drift in the plasma. In analogy to electrorheological fluids, such a system is called electrorheological plasma. In contrast, in the case of an external DC field, no string formation has been observed. Therefore, turning gradually the AC field into a DC field, a phase transition from a string-like electrorheological to an isotropic dusty plasma is expected. A molecular dynamics (MD) simulation assuming a superthermal ion drift is performed for studying this phase transition. A superthermal ion drift in an external electric field could be realized in a future microgravity experiment with complex plasmas proposed for the ISS. In this case, the MD simulation presented here predicts a crossover transition from a string fluid to an isotropic system if the AC field is turned into a DC field. The details of the transition depend on the gas pressure, particle size, and particle density. A microscopic explanation due to particle collisions for the phase transition could be identified from the simulation.