Field Aligned Currents and Aurora During the Terrestrial Alfven Wing State

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2502.16309v3.pdf (1.42 MB)

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http://arxiv.org/abs/2502.16309

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https://doi.org/10.48550/arXiv.2502.16309
 http://hdl.handle.net/11603/37906

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UMBC Faculty Collection
UMBC Goddard Planetary Heliophysics Institute (GPHI)

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https://orcid.org/0000-0001-8702-5806

Date

2025-03-11

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journal articles
postprints
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Citation of Original Publication

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This work was written as part of one of the author's official duties as an Employee of the United States Government and is therefore a work of the United States Government. In accordance with 17 U.S.C. 105, no copyright protection is available for such works under U.S. Law.
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Subjects

Physics - Space Physics

Abstract

When sub-Alfv´enic (Alfv´en Mach number MA < 1) plasmas impact Earth, the magnetosphere develops Alfv´en wings. A Multiscale Atmosphere Geospace Environment (MAGE) global simulation of the April 2023 geomagnetic storm, validated against Active Magnetosphere and Planetary Electrodynamics Response Experiment (AMPERE), reveals the mechanism of field-aligned current (FAC) generation and auroral precipitation for the terrestrial Alfv´en wings. Simulation and observations show northern hemisphere planetward flowing auroral electrons (negative FAC) are predominantly at magnetic local times (MLTs) 8-12. Just before the wings formed, solar wind conditions were similar and MA ∼ 1.4, yet the same FAC system extended from 9-18 MLT. Flow vorticity drives FACs at the boundary of the Alfv´en wings and unshocked solar wind. The Alfv´en wing shape presents a different obstacle to the solar wind compared to typical lobe fluxes, producing the unique FAC and auroral patterns. New insights about Alfv´en wing FACs will help to understand auroral features for exoplanets inside their host star’s Alfv´en zone