Impact of the Out-of-Plane Flow Shear on Magnetic Reconnection at the Flanks of Earth's Magnetopause

TL;DR

This study uses kinetic simulations to show that out-of-plane flow shear at Earth's magnetopause enhances magnetic reconnection rates and energy conversion, especially on the dusk side, improving understanding of solar wind-magnetosphere interactions.

Contribution

It provides the first systematic analysis of how out-of-plane flow shear influences asymmetric reconnection at Earth's magnetopause using kinetic simulations.

Findings

Reconnection rate increases with out-of-plane flow shear.

Dusk side reconnection is more affected than dawn side.

Out-of-plane shear squeezes the diffusion region and boosts energy conversion.

Abstract

Magnetic reconnection changes the magnetic field topology and facilitates the energy and particle exchange at magnetospheric boundaries such as the Earth's magnetopause. The flow shear perpendicular to the reconnecting plane prevails at the flank magnetopause under southward interplanetary magnetic field (IMF) conditions. However, the effect of the out-of-plane flow shear on asymmetric reconnection is an open question. In this study, we utilize kinetic simulations to investigate the impact of the out-of-plane flow shear on asymmetric reconnection. By systematically varying the flow shear strength, we analyze the flow shear effects on the reconnection rate, the diffusion region structure, and the energy conversion rate. We find that the reconnection rate increases with the upstream out-of-plane flow shear, and for the same upstream conditions, it is higher at the dusk side than at the dawn side. The diffusion region is squeezed in the outflow direction due to magnetic pressure which is proportional to the square of the Alfv\'en Mach number of the shear flow. The out-of-plane flow shear increases the energy conversion rate J \cdot E', and for the same upstream conditions, the magnitude of J \cdot E' is larger at the dusk side than at the dawn side. This study reveals that out-of-plane flow shear not only enhances the reconnection rate but also significantly boosts energy conversion, with more pronounced effects on the dusk-side flank than on the dawn-side flank. These insights pave the way for better understanding the solar wind-magnetosphere interactions.