4103 20190206193401.0 SEMIN-2019-0017 Katsiyannis, Thanassis The detection of ultra-relativistic electrons in low Earth orbit 2019 2019-02-06 By combining LYRA and Energetic Particle Telescope (EPT) observations for an overlapping period of time, we identified the detection of highly relativistic 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. STCE ROB thanassis.katsiyannis@observatoire.be SEMIN