Particle in Cell Modeling of Positively Biased Probes in Overdense ExB drifting Plasmas.

Supersonic, ExB flow past a positively biased probe in an overdense plasma is simulated in three dimensions using the Particle In Cell (PIC) method. These simulations are relevant to the questions of anomalously high current seen in orbital experiments as well as being of basic diagnostic interest for probes used is high desnity, rapidly flowng plasmas. The problem of anonymously high currents drawn by biased probes has been known since the tether experiments flown on the Space Shuttle. Cooke et al proposed a theoretical explanation for the anomalously high currents seen in the tether experiments. Modeling the system presents a challenge because the problem involves kinetic effects in an overdose plasma and if fundamentally 3D. We present results of directly modeling this system using a PIC simulation and compare the results to the theoretical model given by Cooke et al.