Intensity of relativistic electron microbursts and their impact on the radiation belts

Abstract:

We investigate the distribution of relativistic electron microburst flux magnitude in the Earth’s outer radiation belts. We use an automated detection algorithm (published in Blum et al., [JGR, 2015]) on low-altitude SAMPEX HILT >1 MeV electron flux observations. This algorithm provides both event detection and precipitating intensity measurements. From this algorithm we have a large database of relativistic microburst events stretching across 1996 – 2007 which we have used to determined relativistic microburst properties. The HILT instrument samples different pitch angle distributions over different parts of the world, such that in different regions HILT is dominated by either trapped, drift loss cone or bounce loss cone fluxes [Dietrich et al., JGR, 2010]. Therefore, we limit our relativistic microburst flux magnitude analysis to the North Atlantic region, where HILT only samples the bounce loss cone. We present statistics of the relativistic microburst flux intensity in this region. It is thought that relativistic microbursts are a result of the pitch angle scattering of trapped outer radiation belt electrons by either whistler mode chorus waves [Thorne et al., JGR, 2005] or EMIC waves [Omura and Zhao, JGR, 2013]. We compare the L and MLT distribution of the relativistic microburst flux magnitude in the North Atlantic region to the chorus and EMIC wave activity. We note that the regions of high flux intensity of the relativistic microbursts partially coincides with the regions of high amplitude whistler mode chorus waves. Regions of high flux intensity relativistic microbursts also coincide with regions of frequent and strong EMIC waves. Lastly, we investigate the overall impact of the relativistic electron microbursts on the trapped relativistic electron populations in the radiation belts.