[P-EM13] Dynamics of the Inner Magnetospheric System

[PEM13-P18] Numerical Modeling of Particle Dynamics during Dipolarization Events

*Kirolosse M. Girgis¹, Tohru Hada¹, Kaiti Wang², Fumiko Otsuka³, Akimasa Yoshikawa^1,4 (1.International Research Center for Space and Planetary Environmental Science (i-SPES), Kyushu University, 2.Aerospace Engineering Department, Tamkang University, Taiwan, 3.Department of Earth System Science and Technology (ESST), Interdisciplinary Graduate School of Engineering Science (IGSES), Kyushu University, 4.Department of Earth and Planetary Sciences, Kyushu University)

Keywords:Dipolarization, Substorm, Test Particle Simulations, Particle Dynamics

We developed a test particle simulation code to examine the particle dynamics during three dipolarization events during substorm time detected by the THEMIS mission. We computed the trajectories and the acceleration levels of 20 keV electrons, protons, and oxygen ions with different initial pitch angles and L-shells by implementing the guiding center model and the full Lorentz particle motion, utilizing an auto-switch between both methods based on the adiabatic trapping condition. We adopted the Tsyganenko model (TS05) and the IGRF-12 to reproduce the time-varying magnetic field model with the corresponding inductive and polarized electric fields. Furthermore, we included the effects of the pitch angle scattering and the substorm current wedge current model.
Our preliminary simulation results confirmed the particle energization in the nighttime magnetosphere during dipolarization. The inclusion of a strong pitch angle scattering model resulted in a 10% protons injection in the outer radiation belt region, whereas the substorm current wedge model led to a 20% protons injection.
Our findings highlight the substorm effects on the radiation belt population and its impact on the near-Earth environment.