Observations of Electron Fluxes in the Radiation Belts with PROBA-V/EPT at Polar Low Earth Orbit and Van Allen Probes/MagEIS at Near Equatorial Elliptical Orbit

Abstract

The electron fluxes in the outer radiation belt during and after geomagnetic storms were investigated using the EPT (Energetic Particle Telescope) instrument on board the ESA PROBA-V satellite at a polar LEO (Low Earth Orbit) at 820 km of altitude and compared with simultaneous observations of the instrument MagEIS on board the NASA Van Allen Probes circulating on a low inclination elliptical orbit ranging from 600 to 30 600 km.We find that the equatorial trapped electron fluxes observed at MEO (Medium Earth Orbit) are higher than at LEO. Below 1 MeV, maximal fluxes differ by ~2 orders of magnitude. However, the EPT ultra-relativistic flux (>2.4 MeV) is much lower than the Van Allen Probes flux at 2.33 MeV, by 4 to 5 orders of magnitude. We also observe that the outer belt is quite isotropic during quiet times, contrary to the inner belt. During storms (here, the big storm of 23 June 2015), the dropout and flux increase observed at LEO and MEO present very similar shapes.