Speaker
Description
Paulikas and Blake first approached the relationship between relativistic electron flux and solar wind speed in late 1979 and found a linear correlation when considering averages of solar wind speed and geosynchronous relativistic outer radiation belts electron flux for three different time intervals (1 day, 27 days, and 180 days). Many years later, Reeves et al., 2011 expanded the analyses using 20 years of data from Los Alamos National Laboratory (LANL) geosynchronous energetic particles and concluded that instead of a linear correlation, the relativistic electrons at the geosynchronous orbit follow a triangular probability distribution. In this distribution, the highest electron flux at geosynchronous orbit is independent of the solar wind speed; otherwise, the lower limit does show a solar wind velocity dependence. These works brought several implications for the outer radiation belt studies in geosynchronous orbit. Many important advances came after to explain how solar wind speed can drive the Earth's magnetosphere. In this work we analyzed the inner portion of the outer radiation belts using the Van Allen Probes era measurements to investigate the region deeper than the geosynchronous orbit, i.e., below L = 5.5, using electron flux measurements from 1 MeV to 5 MeV together with ULF wave measurements. Solar wind speed data are provided by the ACE satellite. We compared the relationship of the three distinct energy channels (1.8 MeV, 3.4 MeV, and 5.2 MeV) of relativistic electron fluxes observed in three distinct regions of the outer radiation belt, L = 3.5, 4, and 5. We found that whatever the L-shell or energy range, the electron flux follows a triangular distribution function. Also, we found that in periods of most HSS events, the electron fluxes are consistently higher. Then we discuss the contribution of the ULF waves under these conditions. These results contribute to a better understanding of the solar wind driving the outer radiation belts' variation in the inner magnetosphere.
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