A statistical approach to determining energetic outer radiation-belt electron precipitation fluxes

Sub-ionospheric radio-wave data from an AARDDVARK receiver located in Churchill, Canada, is analysed to determine the characteristics of electron precipitation into the atmosphere over the range 3 < L 30 keV precipitation flux determined by the AARDDVARK technique was found to be ±10%. Peak >30 keV precipitation fluxes of AARDDVARK-derived precipitation flux during the main- and recovery-phase of the largest geomagnetic storm, that started on 04 August 2010, were >105 el. cm-2 s-1 sr-1. The largest fluxes observed by AARDDVARK occurred on the dayside, and were delayed by several days from the start of the geomagnetic disturbance. During the main phase of the disturbances nightside fluxes were dominant. Significant differences in flux estimates between POES, AARDDVARK and the riometer were found after the main phase of the largest disturbance, with evidence provided to suggest that >700 keV electron precipitation was occurring. Currently the presence of such relativistic electron precipitation introduces some uncertainty in the analysis of AARDDVARK data, given the assumption of a power-law electron precipitation spectrum.

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