Spacecraft potential during an active experiment: a comparison of experimental results with a simple model

Abstract. The Active Plasma Experiment (APEX) used intensive electron beam and/or a release of the low-energy Xenon plasma to study dynamic processes in the magnetosphere and upper ionosphere. It was shown by Prech et al. (1999) that the release of the Xe plasma increases the spacecraft potential when the ambient plasma density is low, but decreases it when the density is high enough. In the present paper, a simple computer model of the dust particle charging has been adapted for a calculation of the potential difference between a planar probe and a spherical satellite moving in the ionospheric plasma. The influence of a quasineutral plasma emission on the measured spacecraft potential difference is discussed and the calculated results are compared with experimental data from the APEX project.

Key words. Ionosphere (active experiments)