Plasma response to high potential satellite in electrodynamic tether system

We study plasma responses to a high potential satellite in the electromagnetic tether system with the aid of two-dimensional electromagnetic particle computer experiments. In the computer experiments, one conducting body representing the satellite is placed in the center of the simulation plane in the vehicle frame. The satellite potential φs is fixed to be higher than the space potential of the surrounding plasma. The transient process of the plasma response to the satellite and the spatial profiles of plasma density and of plasma current are examined. Due to the high potential, an electron sheath and an ion cavity, are formed around the satellite. The ion cavity is extended downstream by the ambient plasma flow. In the direction perpendicular to Bo, the density profile of the plasma flow, shows asymmetric distortion caused by the deceleration of the ambient plasma owing to the intense E x B effect. An intense transient current is observed followed by an exponentially decreasing current. The current flows along and across Bo. The cross-field current is mainly produced by the electron E x B drift motion around the satellite. The current-voltage characteristics of the satellite in the steady state are examined by changing the satellite potential up to eφs/κBTe ≅ 103 and comparing to the classical theories. The average current obtained by the computer experiments is between that predicted by the Langmuir theory and that predicted by the single particle theory. From eφs/κBTe ≅ 101 to 103, the theory based on the constant density model provides a good estimate of the upper bound of the current flowing from the satellite. 35 refs., 12 figs