Speaker
Description
The Van Allen radiation belts are governed by a delicate balance of production and loss processes operating over timescales from fractions of a second to thousands of years. At Earth, these structures consist of a relatively stable inner belt and a highly dynamic outer belt, separated by the slot region. This region is typically depleted of high-energy fluxes and is regarded as a safe zone for satellite operations. Access of multi-MeV electrons into the slot is rare, with the extreme space weather events of 2003 (solar cycle 23) and 2024 (solar cycle 25) serving as well-known examples. Here, using a newly calibrated dataset from solar cycle 22 from the CRRES mission, we identify multiple additional cases where the slot region was flooded with electrons up to multi-MeV energies. Remarkably, these events occurred during strong but non-extreme geomagnetic storms, raising fundamental questions about the mechanisms that enable slot filling to occur. From these observations, we derive the first definitive loss timescales for multi-MeV electrons in the slot region and further examine relativistic electron loss rates in both the inner and outer belts. Finally, we show that non-equilibrium pitch-angle distributions can alter decay rates by up to an order of magnitude, independent of geomagnetic activity, further highlighting the need to account for non-equilibrium effects to accurately model electron fluxes in the inner zone.
