3564 20180920143646.0 POSTER-2018-0043 Katsiyannis, A.C. The detection of ultra-relativistic electrons in low Earth orbit by the LYRA instrument on board the PROBA2 satellite 2018 2018-05-20 The Large Yield RAdiometer (LYRA) is an ultraviolet radiometer on-board ESA's PROBA2 micro-satellite. Since its 2009 launch it observes the Sun in four different passbands, chosen for their relevance to solar physics, aeronomy and space weather. Flying on an altitude of 725 km, LYRA proved to be an excellent flare monitor and is involved in the analysis of the atmospheric composition of the Earth. We present the analysis of energetic particles, indirectly detected by LYRA 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. 2BRAIN_SOL3CAM/ 2BRAIN_SOL3CAM/ 2BRAIN_SOL3CAM STCE Dominique, M. Pierrard, V. Lopez Rosson, G. Triennial Earth Sun Summit 2018, Leesbourg, Virginia, USA thanassis.katsiyannis@observatoire.be https://connect.agu.org/tess2018/home 1685964 http://publi2-as.oma.be/record/3564/files/poster_tess18.pdf 15613 http://publi2-as.oma.be/record/3564/files/poster_tess18.gif?subformat=icon icon 18364 http://publi2-as.oma.be/record/3564/files/poster_tess18.jpg?subformat=icon-180 icon-180 CPOSTER