Polarized supersonic plasma flow simulation for charged bodies such as dust particles and spacecraft

摘要

When an object such as a dust particle or spacecraft is immersed in a plasma flowing at a supersonic speed, an asymmetric screening potential forms around that object. The asymmetry is especially pronounced on the downstream side, with an ion rarefaction in the wake followed by an ion focus region. This polarized screening potential helps explain recent laboratory results with dusty plasmas, where collective interparticle effects were shown to be asymmetric. Using an electrostatic fluid simulation with cold ions and Boltzmann electrons, we have simulated the flow around spherical and cylindrical bodies, with and without a negative potential bias. Here, the flow speed v0 is assumed to be supersonic (faster than ion acoustic) and mesothermal (vTi v0 vTe). A numerical method is used, with a diffuse object that simulates the ion loss and space charge on an object's surface. This works with one or many objects, of any shape. We present solutions for systems of one and two particles in a simulation box, with periodic boundary conditions that help reveal collective effects.