Effects of small-scale plasma disturbance on the IKB-1300 spacecraft potential

The potential of the Intercosmos-Bulgaria-1300 satellite launched to the circular orbit at an altitude - 900 km, was measured. The potential was equalized along the satellite surface. The satellite was covered with a conducting screen and the solar cells were covered with a metal coating. The satellite potential varied slightly along the trajectory and in the typical case it was -2 B that corresponds to 5kTe/e. As the satellite crossed the auroral zone the small scale fluctuations of plasma and field parameters were recorded. In this region a sharp decrease of the satellite negative potential is often observed. In this case the potential variations correlate well with the increasing flux of energetic electrons. The observed variations can be explained by secondary electron emission from the satellite surface.