Kinetic simulations of the dynamic magnetotail

The magnetosphere is a dynamic environment that features a complex interplay between fundamental plasma processes. The accessibility of the magnetosphere for detailed satellite measurements makes it an ideal natural laboratory for studying nonlinear magnetized plasma dynamics. At the Earth's bow shock, the impinging solar wind interacts with the magnetospheric plasma through a collisionless shock and magnetic reconnection, resulting in mixing and a turbulent magnetosheath. These disturbances propagate further downstream and can drive instabilities in the Earth's extended magnetotail - potentially resulting in the onset of magnetospheric substorms. After decades of research, the physical mechanism underlying substorm onset remains one of the of the most important unresolved issues in magnetospheric physics. We present progress in using particle-in-cell simulations of the magnetotail that capture the coupling between global and kinetic scales. Our novel simulations use as initial conditions an analytical Vlasov equilibrium that includes both the near-earth dipole and the extended tail regions. We study the impact of solar wind driving on this configuration using 2D and 3D kinetic simulations and compare with previous results from MHD simulations. The competition between tearing and cross-tail ballooning modes is investigated to determine their roles in the onset of magnetospheric substorms. The implications of these simulations for elucidating substorm onset is disussed by direct comparison with satellite measurements.