Theory and modeling of large scale plasmapause surface waves
Author(s)
Type
Journal Article
Abstract
The plasmapause in Earth's magnetosphere represents the boundary between the plasma which co-rotates with the Earth (plasmasphere), and the more tenuous plasmatrough outside. The density change across the plasmapause can be large, changing by approximately 1–2 orders of magnitude depending on the prevailing conditions. This would suggest it to be a location where magnetohydrodynamic (MHD) surface waves can form, and indeed, this has been proposed in previous works to explain ultra-low frequency (ULF) wave observations around the plasmapause location. The main question is how such a large scale surface wave on the plasmapause would be excited. In this paper, we propose a model whereby surface waves at the plasmapause are driven by energy input from the magnetopause through solar wind driving. We derive an analytical form for the amplitude of these surface waves with this new driven boundary condition at the magnetopause. The excitation of these waves is then tested in several MHD simulations, where the model geometry, wavenumbers and temporal dependence of the magnetopause driver are varied. We establish that surface waves on the plasmapause can be excited by driving from the magnetopause, and that this still occurs with impulsive and continuous broadband driving. The azimuthal scale of the wave is a critical factor for this excitation, with longer azimuthal scales more favorable for driving larger amplitude surface waves. This mechanism provides new insight for how large scale and large amplitude ULF waves can access the inner magnetosphere, with potential implications for their interaction with radiation belt particles.
Date Issued
2025-09-01
Date Acceptance
2025-08-19
Citation
Journal of Geophysical Research: Space Physics, 2025, 130 (9)
ISSN
2169-9380
Publisher
American Geophysical Union (AGU)
Journal / Book Title
Journal of Geophysical Research: Space Physics
Volume
130
Issue
9
Copyright Statement
©2025. 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
e2025JA033830
Date Publish Online
2025-08-31