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Abstract:
This study addresses whether a series of strong substorm-associated MeV electron injections can be a crucial contributor to outer-radiation belt enhancement events. We examine an event that occurred on July 10, 2019, where ~2 MeV electron fluxes increased by ~3 orders of magnitude in only ~7.5-hrs under 4 repetitive, strong relativistic electron injections. For this examination, it is essential to precisely separate purely temporal flux changes from spatial variations observed as Van Allen Probes move along their orbits (i.e., orbital effect). Employing a new “hourly snapshot” analysis approach, we uncover unprecedented details of electron flux dynamics that indicates that the overall outer belt enhancement for this event was not continuous but composed of 4 large discrete flux increases primarily driven by the strong injections. These injections appear as sharp flux increases at all energies when a spacecraft is located in the injection region, and the inner-most L of the flux increase is located farther out with increasing energy as expected for injections. Earthward of the injection region, by comparing hourly snapshots for different times, we infer injections and infer temporally-stable fluxes between injections, despite strong and continuous chorus emission. The fast and intermittent, large flux growths imply cumulative outer belt enhancement via repetitive inward radial transport associated with injection-induced electric fields.
