PITCH ANGLE PROPERTIES OF MAGNETOSPHERIC THERMAL PROTONS AND SATELLITE SHEATH INTERFERENCE IN THEIR OBSERVATION.

Cold proton observations from the geosynchronous GEOS 2 satellite are presented to show the pitch angle distribution of the refilling cold ion population found beyond the plasmapause. This refilling cold ion population, which is observed both day and night, flows into the depleted equatorial regions of the flux tubes from the topside ionosphere. The ions have energies between 0. 5 and 3 ev. Unfortunately, these particles have energies comparable to the typical sheath potential; hence these observations are integrally related to the effects of the satellite sheath. In interpreting these data, data and arguments are presented to show that the effects the satellite sheath has on the measurements are qualitatively undersood.