Refilling of the Plasmasphere at Geosynchronous Orbit: Observations and Modeling

Abstract:

The plasmasphere is eroded during increases in the convection electric field which strip off its outer portions and carry them to the dayside magnetopause in a plasmaspheric drainage plume. Once the convection electric field weakens the outer plasmasphere refills from the ionosphere. Observations at geosynchronous orbit (GEO) show that plasmaspheric ions sometimes refill to number densities in excess of 100 cm^-3 within ~48 hours. This observed refilling rate is far in excess of that generally predicted by theoretical models. To study the physics of refilling, a fully-updated version of the SUPIM code is used. We present observations of refilling at GEO alongside a detailed modeling study of the factors governing the refilling process. Suggestions are made for overcoming the disparity between observations and model results.