5:15 PM - 7:15 PM
[PEM13-P23] Research of the acceleration process of electrons at the outer edge of the radiation belt during substorms
Injection of energetic particles is one of the major features of substorms in the inner magnetosphere. Understanding substorm-associated particle injection is crucial, as it may be linked to the modulation of the radiation belt. The bounce-averaged and guiding center approximations are often used to trace the trajectories of energetic particles, but these approximations are limited to the near-Earth region where the magnetic field is dipole-like. In the tail region where the magnetic field is weak and spatiotemporal fluctuations are significant, in particular, during substorm, solving the full equation of motion is required to accurately tracing particle trajectories. We employed the global magnetohydrodynamic (MHD) simulation REPPU, which can reproduce various substorm-related phenomena. However, retrieving magnetic and electric fields at specific points is computationally expensive due to its complex lattice structure. To mitigate this, we precomputed and stored the magnetic and electric fields on a predefined Cartesian coordinate lattice. By this way, the computational cost was significantly reduced. We performed the MHD simulation under the solar wind velocity of 400 km/s and interplanetary space magnetic field IMF Bz of -5 nT, focusing on a substorm with a minimum AL index of ~ -500 nT. Tracing electrons with initial energy of 10 keV, we found that the electrons originating at the geocentric distances of 8-9 RE moved inward to ~7.5 RE within about 30 seconds, accelerating to about 40 keV. In contrast, 10 keV electrons starting from farther distances did not show significant increase in the kinetic energy. We will discuss the dependence on the initial position, energy, and pitch angle, as well as the broader impact of substorms on particle dynamics and changes in the electron fluxes in the inner magnetosphere.