Earth's outer radiation belt electrons: Identifying sources, improving forecasts, and a new particle detector design.

摘要

Earth's outer radiation belt is a highly dynamic region composed primarily of relativistic electrons, which can pose a threat to spacecraft and astronauts. Despite decades of acquiring data and conducting research, the exact mechanisms and relative importance of outer belt electron source, loss, and transport processes are still not fully understood. Here, I follow the full cycle of outer belt electron data, from acquiring it in situ to analysis and practical use. I start by discussing a new instrument designed to measure relativistic particles from a low-cost picosatellite in low-Earth orbit, which will provide complementary data to NASA's Radiation Belt Storm Probes mission. Next, I discuss data analysis studies of the source of relativistic electrons in the outer belt conducted using electron data from existing instruments. I provide a detailed discussion of the results of these studies, which reveal clear evidence that there are two distinct populations of electrons in the outer belt, each with a different source region: (1) low-energy electrons with energy below a few hundred keV and source in the magnetotail, and (2) relativistic electrons with energy greater than around 500 keV that most often have a source within geosynchronous orbit. These results indicate the importance of substorms and wave-particle interactions for the acceleration of relativistic electrons. I finish with the details of an improved forecast system for these electrons, which demonstrates how outer belt electron data are used for practical applications.