Relativistic Microbursts and their Relationship to Observed Plasmapause Location

Relativistic microbursts are short (<1 sec) duration bursts of precipitating relativistic electrons observed in low Earth orbit. Microburst activity is often higher for days following geomagnetic storms and is believed to result from interactions between trapped radiation belt electrons and intense whistler chorus waves. This is thought to be an important process for stormtime depletion of the outer radiation belt and/or an indicator of whistler energization and repopulation of outer belt electrons. These wave-particle interactions are optimized outside the plasmapause, leading to a dependence of microburst locations on plasmapause location. We present results on the location of SAMPEX-observed microbursts with respect to changes in the location of the plasmapause as observed by the DMSP satellites. Innermost microburst locations are well correlated with outermost plasmapause locations, with microbursts located outside the plasmapause. We also discuss the timescale of variations in microburst and plasmapause location.