Kinetic Simulations of Particle Acceleration in the Magnetotail

Magnetospheric substorms are frequent disruptions of the Earth's magnetotail associated with transient features including bursty flows of magnetized plasma and energetic particle acceleration. Using fully kinetic, two-dimensional (2D) and three-dimensional (3D) particle-in-cell simulations starting from an exact magnetotail equilibrium, we model the onset of substorms and reproduce prominent features of observations and models including magnetic reconnection onset, a near-Earth ballooning instability, current sheet flapping, and nonthermal particle acceleration. For the first time in a realistic magnetotail configuration, we use self-consistent particle tracking to analyze the trajectories of nonthermal electrons and ions. We identify the dominant acceleration mechanisms including X-point acceleration, plasmoid mediated acceleration, and betatron acceleration, and compare the energetic particle spectra with observations. We compare the acceleration in 2D and 3D simulations to determine the roles of intrinsically 3D mechanisms, providing new insight into the 3D dynamics of substorms.