Effects of Outer Plasmasphere Processes on Atmospheric Precipitation: A Multipoint Observational Study

Earth's inner and outer radiation belts are surrounded by a natural high intensity radiation environment, composed of high energy and relativistic particles. The dynamic outer plasmasphere overlaps the outer radiation belt beyond L=2.5 and can play a key role in modulating the outer radiation belt. In particular, ambient cold plasma density associated with plasmaspheric structure and density gradients in the plasmasphere boundary layer (PBL) can regulate the occurrence and characteristics of wave-particle interactions (WPI) leading to large changes in precipitation/loss efficiency. These interactions are efficient at scattering high energy particles into the atmospheric loss cone, resulting in spatially localized enhancements in outer radiation belt acceleration and precipitation. We discuss a multi-point observational case study of the relationship of dayside radiation belt precipitation temporal and spatial dynamics to outer plasmasphere processes during a coronal mass ejection driven shock injection and plasmasphere reconfiguration event on 2014-01-09. We combine in-situ magnetosphere diagnostics from the Van Allen Probes A and B spacecraft with in-situ data from multiple BARREL balloons measuring atmospheric precipitation in the afternoon MLT sector, near the Van Allen Probes magnetic footprints. Van Allen Probes and THEMIS E data from their respective EFW instruments determines electric field structure and thermal electron density configurations to L~7. Finally, we place the in-situ diagnostics in a larger context using GPS ground based total electron content observations of L <= 4 wide field plasmaspheric structure and PBL dynamics. We present analysis explaining the observed atmospheric precipitation, and demonstrating the significance of the outer plasmasphere boundary location in processes leading to energetic electron precipitation. Such multi-instrument analysis demonstrates that consideration of interconnected system-level processes leads to a clearer understanding of the characteristics of individual features.