Exploring Outer Radiation Belt Losses From the International Space Station

The precipitation of energetic electrons from the outer radiation belt plays a crucial role in regulating their flux dynamics and influencing ionospheric properties. While theoretical and numerical studies, often based on near-equatorial spacecraft measurements, are essential for assessing the precipitation efficiency, low-altitude observations offer a direct and effective method for monitoring these losses. This study analyzes a new data set of energetic electron precipitation captured by the CALorimetric Electron Telescope (CALET) and the Monitor of All-sky X-ray Image (MAXI) aboard the International Space Station. By comparing CALET and MAXI measurements with low-altitude observations from ELFIN, we identified three distinct precipitation patterns: those driven by electron scattering from whistler-mode waves, electromagnetic ion cyclotron waves, and field-line curvature scattering (FLCS). Each pattern exhibits unique characteristics, allowing us to construct a statistical picture of precipitation based on CALET and MAXI data. A key finding from this analysis is the substantial contribution of FLCS-driven precipitation within the outer radiation belt. These results highlight the necessity of incorporating FLCS as a significant loss mechanism in radiation belt models.