3576 20180920143409.0 CTALK-2018-0064 Katsiyannis, Athanassios C. The detection of ultra-relativistic electrons in low Earth orbit by the LYRA instrument on board the PROBA2 satellite 2018 2018-11-09 We present the analysis of energetic electrons, indirectly detected at an altitude of ~700 km 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 a prominent dawn-dusk asymmetry. A combination of various magnetospheric mechanisms is proposed as a starting point towards a full quantitative explanation. 2STCE_PHYSSOL/ 2STCE_PHYSSOL/ 2STCE_PHYSSOL STCE Dominique, Marie Pierrard, Viviane Lopez Rosson, Graciela European Space Weather Week 15, Leuven thanassis.katsiyannis@observatoire.be http://www.stce.be/esww15/ Contributed CTALKCONT