Superposition of doppler-shifting magnetopause Kelvin-Helmholtz modes through dynamic mode decomposition of a global MHD simulation
Author(s)
Type
Journal Article
Abstract
The Kelvin-Helmholtz instability (KHI) mediates the viscous-like solar-terrestrial interaction by generating magnetopause surface waves that quickly become non-linear. Basic theory predicts the locally most-unstable linear wave dominates. However, Kelvin-Helmholtz is a broad, convective instability that also amplifies waves originating upstream. We address this conundrum by applying dynamic mode decomposition to a Gorgon global magnetohydrodynamic simulation of the KHI. While distinct modes quickly grow at points along the magnetopause, signaling local generation, their energy continues to slowly grow downtail. Thus, a superposition is present along the magnetopause, where the dominant mode is not always the locally fastest-growing. Each mode's wavelength elongates downtail, correlating with the boundary layer flow speed due to the accelerating advective flow around the magnetosphere Doppler shifting the fixed-frequency waves. This may explain why longer wavelengths are observed in the tail than theory predicts and motivates further exploration of tangential inhomogeneities in basic Kelvin-Helmholtz theory.
Date Issued
2026-05-28
Date Acceptance
2026-04-21
Citation
Geophysical Research Letters, 2026, 53 (10)
ISSN
0094-8276
Publisher
Wiley
Journal / Book Title
Geophysical Research Letters
Volume
53
Issue
10
Copyright Statement
© 2026. The Author(s). This is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited.
License URL
Publication Status
Published
Article Number
e2025GL120284
Date Publish Online
2026-05-18