How EDR-related currents close in particle-in-cell simulations

Abstract:

In MMS observation large field-aligned currents are observed in the vicinity of magnetic reconnection. We study whether these currents are locally closed to the extent of the diffusion region, or if they couple to larger scales and thus should be visible in other regions of the magnetosphere-ionosphere system. If they are locally closed, what is their spatial extend, and which process facilitates the transition from parallel flow to perpendicular flow. The parallel currents, carried by electrons, flow along the separatrix as consequence of the Hall magnetic field. The perpendicular closure current is likely supported by protons being less tied to the magnetic flux tubes, ow- ing to their larger larmor radius. To understand the causality and extent of these EDR-related currents we use a high-resolution 2.5D particle-in-cell with enough particles to resolve the necessary variables, including electron inertia terms.