Global Magnetic Reconnection During Sustained Sub-Alfvénic Solar Wind Driving

When the solar wind speed falls below the local Alfvén speed, the magnetotail transforms into an Alfvén wing configuration. A Grid Agnostic Magnetohydrodynamics for Extended Research Applications (GAMERA) simulation of Earth's magnetosphere using solar wind parameters from the 24 April 2023 sub-Alfvénic interval is examined to reveal modifications of Dungey-type magnetotail reconnection during sustained sub-Alfvénic solar wind. The simulation shows new magnetospheric flux is generated via reconnection between polar cap field lines from the northern and southern hemisphere, similar to Dungey-type magnetotail reconnection between lobe field lines mapping to opposite hemispheres. The key feature setting the Alfvén wing reconnection apart from the typical Dungey-type is that the majority of new magnetospheric flux is added to the polar cap at local times 1–3 (21-23) in the northern (southern) hemisphere. During most of the sub-Alfvénic interval, reconnection mapping to midnight in the polar cap generates relatively little new magnetospheric flux.