Resolving Discrepancies in Electron Ring Current Models: The Importance of a Pre-Midnight Loss Process

The ring current, a key feature of Earth's magnetosphere, is enhanced during geomagnetic storms, posing risks to spacecraft through surface charging by 10-50 keV electrons. While extensively studied, accurately modeling storm-time ring current dynamics remains challenging.

We show that existing ring current models significantly overestimate the trapped population of the Earth’s night-side electron ring current at energies between 10 and 50 keV during geomagnetic storms compared to satellite observations. Through analysis of electron drift trajectories, we identify a missing pre-midnight loss process, requiring strong diffusion to match observations. Validation of predicted electron precipitation using low-Earth orbit satellite measurements further supports our findings that strong diffusion is reached in a broad region in the pre-midnight sector.

We further discuss the physics behind this loss process, which has been neglected in previous modeling efforts. Incorporating this loss process in future models is key to accurately predicting the storm-phase electron ring current and its associated space weather hazards.