Flux transfer events in the cusp

Abstract

We use 2.5‐dimensional global hybrid (kinetic ions, fluid electrons) simulations to study the evolution of Flux Transfer Events (FTEs) and their interaction with the cusp during their poleward motion. A southward pointing interplanetary magnetic field is considered. It results in low‐latitude, time‐dependent reconnection and the formation of multiple FTEs with a variety of sizes ranging from a few hundred to thousands of km. FTEs are found to travel along the magnetopause surface with velocities exceeding the surrounding magnetosheath by ∼1 local Alfven speed. As a result, a slow mode bow wave and a pile up of plasma and magnetic field precede larger, but not smaller, FTEs. As an FTE encounters the cusp, a secondary magnetic reconnection is initiated which ultimately leads to its disintegration as it moves to higher latitudes. Both the slow mode bow wave and reconnection accelerate plasma into the cusp and enhance the flux of energetic ions in this region. The downward flux of ions at a given energy moves poleward in time, exhibiting characteristics similar to the poleward moving auroral forms previously attributed to FTEs.