Dynamics of Megaelectron Volt Electrons Observed in the Inner Belt by PROBA-V/EPT

TL;DR

This study uses high-resolution satellite data to analyze the behavior and injection mechanisms of relativistic electrons in Earth's inner and outer radiation belts during geomagnetic storms, revealing new insights into their dynamics and residence times.

Contribution

It provides detailed observations of MeV electron injections into the inner belt during storms, highlighting the energy-dependent inward shift of outer belt electrons and their residence times.

Findings

MeV electrons are observed in the inner belt during storms, not due to proton contamination.

Electron flux peaks shift inward with energy during storms.

Relativistic electrons are injected into the inner belt and their residence times vary.

Abstract

Using the observations of the EPT (Energetic Particle Telescope) onboard the satellite PROBA-V we study the dynamics of inner and outer belt electrons from 500 keV to 8 MeV during quiet periods and geomagnetic storms. This high time-resolution (2 sec) spectrometer operating at the altitude of 820 km on a low polar orbit is providing continuously valuable electrons fluxes for already 5 years. We emphasize especially that some MeV electrons are observed in low quantities in the inner belt, even during periods when they are not observed by Van Allen Probe (VAP). We show that they are not due to proton contamination but to clear injections of particles from the outer belt during strong geomagnetic storms of March and June 2015, and September 2017. Electrons with lower energy are injected also during less strong storms and the L-shell of the electron flux peak in the outer belt shifts inward with a high dependence on the electron energy. With the new high resolution EPT instrument, we can study the dynamics of relativistic electrons, including MeV electrons in the inner radiation belt, revealing how and when such electrons are injected into the inner belt and how long they reside there before being scattered into the Earth's atmosphere or lost by other mechanisms.