The Evolutions of the Seed and Relativistic Electrons in the Earth's Outer Radiation Belt During the Geomagnetic Storms: A Statistical Study

Using the Van Allen Probes data, we statistically study the evolutions of the seed and relativistic electrons in the Earth's outer radiation belt during the storms. Based on the different storm intensities and durations of the main phase, the storm events are divided into "moderate and short (MS) events," "moderate and long (ML) events," "strong and short (SS) events," and "strong and long (SL) events." The results from a superposed epoch analysis show that (a) For most MS and SS events, the seed electron fluxes can exceed pre-storm levels, and enhanced fluxes mainly occur around the storm peak. (b) For the ML and SL events, the seed electron fluxes greatly exceed pre-storm levels by more than an order of magnitude, and enhanced fluxes mainly occur during the main phase. (c) For most MS events, MeV electron fluxes are difficult to return to or exceed pre-storm levels. While MeV electron fluxes at some L* shells for some SS events can exceed pre-storm levels. (d) For most ML or SL events, MeV electron fluxes at L* =4.0 or =3.5 can exceed pre-storm levels, and enhanced fluxes mainly start to occur from the main phase. These results suggest that the duration of the main phase and storm intensity play important roles in the evolutions of the seed and MeV electrons in the Earth's outer radiation belt during the storms. These are important for our further understanding of the electron dynamics of the outer radiation belt.