Current Collection in Plasmas by a Static Bare Tether

Abstract

Current collection in plasmas by a static bare tether is studied. Considering the geometry effect, we modify the static Parker-Murphy current collection model to accommodate a cylindrical probe. It is shown that a long cylindrical configuration (length is much greater than diameter) can collect more current than the spherical configuration whose effective surface area and surface potential are identical. However, when the cylinder is not long (length and diameter are same order), it collects less current than the effective sphere. This indicates that Myers et al. might over estimate the PM current when they neglected the geometry effect. Compared to the orbit limit model and the chamber experiment, our predictions are in the range of the adiabatic limits and the upper-bound currents obtained by Rubinstein and Laframboise. It shows that the present results are in agreement with the bare tether chamber test experimental data given by Sorenson, Stone, and Wright. In addition we have applied this model to study the IR drop and the orientation effects which are important in the space condition.