Earth's Alfv\'{e}n Wings: Unveiling Dynamic Variations of Field-line Topologies with Electron Distributions

TL;DR

This study uses MMS data to analyze electron distribution signatures during Earth's magnetosphere transformation into Alfvén wings caused by a CME, revealing dual wing reconnection and bursty magnetic reconnection evidence.

Contribution

First characterization of electron distribution signatures during Earth's Alfvén wing formation with MMS measurements, highlighting dual wing reconnection processes.

Findings

Electron signatures include strahl electrons and energetic keV electrons along wing field lines.

Distribution signatures indicate dual wing reconnection between dawn-dusk Alfvén wings and IMF.

Evidence of bursty magnetic reconnection under northward IMF conditions.

Abstract

The magnetic cloud (MC) of the Coronal Mass Ejection on April 24, 2023, contains sub-Alfv\'{e}nic solar wind, transforming Earth's magnetosphere from conventional bow-shock magnetotail configuration to Alfv\'{e}n wings. Utilizing measurements from the Magnetosphere Multiscale (MMS) mission, we present for the first time electron distribution signatures as the spacecraft traverses through various magnetic topologies during this transformation. Specifically, we characterize electrons inside the sub-Alfv\'{e}nic MC, on the dawn-dusk wing field lines and on the closed field lines. The signatures include strahl electrons in MC regions and energetic keV electrons streaming along the dawn and dusk wing field lines. We demonstrate the distribution signatures of dual wing reconnection, defined as reconnection between dawn-dusk Alfv\'{e}n wing field lines and the IMF. These signatures include four electron populations comprised of partially-depleted MC electrons and bi-directional energetic electrons with variations in energy and pitch-angle. The distributions reveal evidence of bursty magnetic reconnection under northward IMF.