With contributions from Benck, S. , Lopez-Rosson, G.  and Pierrard, V. 
 Center for Space Radiations, UCL, Louvain-La-Neuve
Since May 2013, the Energetic Particle Telescope (EPT) is orbiting on a polar LEO at 820 km altitude, on board of PROBA-V (Cyamukungu et al., 2014 & Pierrard et al., 2014 respectively for the instrument description & preliminary results of the EPT). The fluxes of trapped electrons are measured by the EPT in 7 different energy channels ranging from 0.5 MeV to 20 MeV, We present the observations collected during the geomagnetic storm of 17 March 2015 (Dst: -231 nT), as well as during the two smaller storms in December 2015 (Dst = -45 nT & -150 nT).
During the main phase of these storms, typical drop-outs are observed at low altitudes in all energy channels, in outer Radiation Belt drift shells (L > 4). Some of these drop-outs are followed by the penetration of relativistic electrons down to L = 2. The strong injection event of March 2015 filled up the slot region between the inner and outer Radiation Belts, for a period of a few days, as illustrated by the standard (L-t) maps that will be presented.
These standard (L-t) maps also indicate that the outer belt electron fluxes were significantly enhanced after the geomagnetic storm, as compared to before the storm of March 2015. At the same time the MAGEIS/VAP-B detector, on board Van Allen Probes B flying along a GTO orbit, also observed enhanced relativistic electron fluxes after this storm event.Similar post-storm enhancements of energetic electron fluxes had been observed/reported earlier, but they had never been measured simultaneously (i) at low altitudes (along a LEO alike that of EPT/PROBA-V), and (ii) at large radial distances in the equatorial region (along a GTO orbit like that of MAGEIS/VAP-B).
We will indicate how Betatron deceleration associated with the uplift of mirror points (during storm main-phases), and Betatron acceleration associated with a downward return of mirror points (during the recovery-phases) can explain the flux variations observed with the EPT. Indeed, the flux variations observed at low altitudes with the EPT are the consequence of Betatron deceleration and acceleration (also called Dst-effect) induced by the growth of the Ring Current, and by its subsequent decay during the slower recovery phase.The effect of concomitant non-resonant wave-particle interactions of whistler waves and
ULF waves with trapped electrons during main-phases and recovery-phases, can account for enhancements of electron fluxes observed in the outer belt following some geomagnetic storm events. This is an alternative to the acceleration mechanism by resonant wave-particle interactions often invoked. Unlike the usual (B-L) flux maps, the EPT flux distributions are displayed in a new magnetic invariant coordinate system [Invariant-altitude (h_inv) & Magnetic-latitude (MagLat)] ; this coordinate system, which was introduced by Cabrera and Lemaire (2007), offers the key advantage to display more clearly and obviously low altitude distributions of trapped RB particles within McIlwain's reference dipole. Our (h_inv - MagLat) flux maps did enable us to uncover transient trapped electron populations during the main-phases of geomagnetic storms.