Storm-Time Ring Current Seen by IMAGE

Mei-Ching Fok
USRA at NASA/GSFC

Since the start of science operations, IMAGE has observed several magnetic storms. Some of them were very intense, and at least one produced double-dip Dst. The Medium and High Energy Neutral Atom Imagers (MENA and HENA) on board IMAGE captured the ring current development during these storms. Most of the time the ring current evolved in a typical way: initial buildup near midnight, westward drifting to the dayside, and subsequent decay at recovery phase. The images suggest very full loss cones during the main phase, evolving during decay toward peak fluxes at large pitch angles. However, some images revealed uncommon features, e.g., ring current enhancement at dawn during early storm main phase. We will present images seen by MENA and HENA during these storms and attempt to understand the distinct features using ring current simulations based on a kinetic model that includes pitch-angle distribution and realistic dynamic electric field structures.