Determining When, Where, and Why Radiation Belt Dropouts Do and Don't Occur

While our understanding of electron acceleration mechanisms in Earth's radiation belts has greatly increased over the past decade, quantitative physics-based understanding of loss mechanisms remains elusive. In particular, numerous questions remain regarding the causes of rapid radiation belt depletions or “dropouts”, which are typically observed during the main phase of geomagnetic storms. Losses to the magnetopause often cannot fully account for depletions observed across the outer radiation belt and while diffusion models can now reproduce observed acceleration events quite accurately, radiation belt dropouts are less well-captured.