Field-Aligned Current Structures during the Terrestrial Magnetosphere's Transformation into Alfven Wings and Recovery

TL;DR

This paper reports the first direct measurements of current structures during an Alfven Wing formation in Earth's magnetosphere caused by a CME event, revealing unique anti-field-aligned and electron-driven currents.

Contribution

It provides novel in situ observations of current structures during Alfven Wing development, enhancing understanding of magnetosphere dynamics during sub-Alfvenic solar wind conditions.

Findings

Identification of two distinct current structures associated with Alfven Wings

Discovery of currents that are more anti-field-aligned and electron-driven than typical magnetopause currents

Insights into magnetosphere disruption caused by Alfven Wing formation

Abstract

On April 24th, 2023, a CME event caused the solar wind to become sub-Alfvenic, leading to the development of an Alfven Wing configuration in the Earth's Magnetosphere. Alfven Wings have previously been observed as cavities of low flow in Jupiter's magnetosphere, but the observing satellites did not have the ability to directly measure the Alfven Wings' current structures. Through in situ measurements made by the Magnetospheric Multiscale (MMS) spacecraft, the April 24th event provides us with the first direct measurements of current structures during an Alfven Wing configuration. We have found two distinct types of current structures associated with the Alfven Wing transformation as well as the magnetosphere recovery. These structures are observed to be significantly more anti-field-aligned and electron-driven than typical magnetopause currents, indicating the disruptions caused to the magnetosphere current system by the Alfven Wing formation.