Temporal evolution of proton precipitation associated with the plasmaspheric plume

The temporal evolution of afternoon sector proton precipitation observed by a global auroral imager is examined in detail for two case events. We focus on precipitation regions that are magnetically mapped to the plasmapause and plasmaspheric plume regions. The spatial and temporal variation of the pume-associated precipitation, including its relationship to the main proton oval, is dependent on the prevailing solar wind and magnetospheric driving conditions. Two contrasting events are presented here in association with 1) a substorm injection and 2) a northward IMF turning. We find that proton precipitation within the plasmaspheric plume is a persistent feature during geomagnetically disturbed periods, but the precipitation regions only appear latitudinally detached from the main proton oval under specific conditions. The evolution in both time and space of the plume-associated precipitation regions is consistent with theoretical predictions for EMIC wave scattering of protons in the ring current energy range.