The detection of ultra-relativistic electrons in low Earth orbit by the LYRA instrument on board the PROBA2 satellite

Athanassios Katsiyannis, Observatoire Royal de Belgique, Brussel, Belgium, Marie Dominique, Royal Observatory of Belgium, Brussels, Belgium, Viviane Pierrard, Belgian Institute for Space Aeronomy, Brussels, Belgium and Graciela Lopez Rosson, Royal Belgian Institute for Space Aeronomy, Space Physics, Brussels, Belgium
Abstract:
We present the analysis of energetic particles, indirectly detected by the Large Yield RAdiometer (LYRA) instrument on board ESA's Project for On-board Autonomy 2 (PROBA2) satellite in the form of microbursts of <10 ms, with a phenomenon duration of 100 s. Combining Energetic Particle Telescope (EPT) observations with LYRA data for an overlapping period of time, we identified these particles as electrons with an energy range of 2 to 8 MeV. The observed events are strongly correlated to geo-magnetic activity and appear even during modest disturbances. Additionally, they are well confined geographically within the L=4-6 McIlwain zones, and they show prominent dawn-dusk and day-night asymmetries. A combination of wave-particle interaction mechanisms is proposed as a starting point towards a full quantitative explanation.
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