Field‐Aligned Currents Originating From the Magnetic Reconnection Region: Conjugate MMS‐ARTEMIS Observations

Abstract

AbstractNear‐Earth magnetic reconnection reconfigures the magnetotail and produces strong plasma flows that transport plasma sheet particles and electromagnetic energy to the inner magnetosphere. An essential element of such a reconfiguration is strong, transient field‐aligned currents. These currents, believed to be generated within the plasma sheet and closed at the ionosphere, are responsible for magnetosphere‐ionosphere coupling during substorms. We use conjugate measurements from Magnetospheric Multiscale (MMS) at the plasma sheet boundary (around x ∼− 10RE) and Acceleration, Reconnection, Turbulence and Electrodynamics of the Moon's Interaction with the Sun (ARTEMIS) at the equator (around x ∼− 60RE) to explore the potential generation region of these currents. We find a clear correlation between the field‐aligned current intensity measured by MMS and the tailward plasma sheet flows measured by ARTEMIS. To better understand the origin of this correlation, we compare spacecraft observations with results from 3‐D particle‐in‐cell simulations of magnetotail reconnection. The comparison reveals that field‐aligned currents and plasma flows start, wax, and wane due to the development of a reconnection region between MMS (near‐Earth) and ARTEMIS (at lunar distance). A weak correlation between the field‐aligned current intensity at MMS and earthward flow magnitudes at ARTEMIS suggests that distant magnetotail reconnection does not significantly contribute to the generation of the observed near‐Earth currents. Our findings support the idea that the dominant role of the near‐Earth magnetotail reconnection in the field‐aligned current generation is likely responsible for their transient nature, whereas more steady distant tail reconnection would support long‐term field‐aligned current system.