Assessing the Roles of Kinetic Ballooning Instability and Magnetotail Reconnection in Triggering Substorms

The interplay of physical mechanisms that leads to the onset of explosive disruption of the Earth’s magnetotail – i.e., substorms – has long eluded understanding. Observational evidence suggests that substorm onset auroral signatures are strongly associated with current sheet disruption in the dipole-tail transition region. One way such disruption can occur is via an interplay between magnetic reconnection further down the tail, and the kinetic ballooning instability (KBI) in the near-Earth region. We have modelled reconnection, its earthward jet front, and the disruption of the near-Earth current sheet with the 3D PIC code OSIRIS¹. These novel simulations employ an exact kinetic equilibrium for the nightside magnetosphere, and capture earthward transients commonly observed pre-substorm onset – e.g., dipolarization fronts (DFs). Our model suggests a strong association between the disruption of earthward-propagating DFs and KBI onset. In this work, we compare our simulations with substorm-associated DFs captured by NASA’s Magnetospheric Multiscale (MMS) mission to assess the exact roles of KBI and magnetotail reconnection in triggering substorms.



¹ S. R. Totorica et al, arXiv:2201.06193 [physics.space-ph]