Global Characteristics of Drift Magnetopause Loss

The flux level of radiation belt electrons is maintained by a competition of multiple source and loss processes occurring within the magnetosphere and driven both by the solar wind and internal processes. While most of the research community's attention has focused on understanding electron flux enhancements, data from the geosynchronous regions have uncovered many unexplained rapid flux decreases. One possible mechanism for these flux dropouts is the drift loss of electrons to the magnetopause boundary. Using magnetospheric configurations predicted by the Tsyganenko model, we found that 80% of geosynchronous flux dropouts are on open drift paths, a signature of magnetopause shadowing. In one magnetopause-shadowing event, six geosynchronous satellites (GOES and LANL), spanning a wide range of local times, observed relativistic electron dropouts within a several hour interval. The time sequence of the magnetopause-shadowing signature at each geosynchronous satellite explained the local-time dependence of dropout onsets observed by Onsager et al. [2002]. Understanding the drift magnetopause loss on a global scale is essential for further quantifying the total electron loss through the magnetopause. Therefore, we will use multi-spacecraft measurements beyond geosynchronous orbit to characterize and quantify the variability of the outer electron belt in concert with magnetopause position. We then analyze the electron dropout onsets at different L shells to estimate the inward radial transport rate of the drift magnetopause loss. Finally, the upcoming Radiation Belt Storm Probes (RBSP) mission will provide exceptional data for a better understanding of this major loss mechanism even when the satellites are well inside the magnetopause location.