Mechanisms that limit potentials on ionospheric satellites

Abstract

For spinning satellites with dielectric coatings it is shown that the currents of rotating charge embedded in the dielectric surface can play a role in limiting the spacecraft ground potential of an ionospheric satellite relative to the surrounding plasma. Such currents, as well as small concentrations of H+, can account for previous discrepancies of more than a factor of 2 between measured and calculated potentials of satellites in the region of the ionosphere where O+ is dominant. More generally, dielectric conduction can also limit the satellite potential. The importance of such small currents as result from spin and conduction stems from the extremely small ion currents impinging on the wakeside of the satellite. Finally, theoretical estimates based on a newly described constant of the motion of a particle indicate that accounting for small concentrations of H+ remove the major discrepancy between calculated and measured currents on the wakeside of the AE‐C satellite.