Auroral, ionospheric and ground magnetic signatures of magnetopause surface modes
Author(s)
Type
Journal Article
Abstract
Surface waves on Earth's magnetopause have a controlling effect upon global magnetospheric dynamics. Since spacecraft provide sparse in situ observation points, remote sensing these modes using ground-based instruments in the polar regions is desirable. However, many open conceptual questions on the expected signatures remain. Therefore, we provide predictions of key qualitative features expected in auroral, ionospheric, and ground magnetic observations through both magnetohydrodynamic theory and a global coupled magnetosphere-ionosphere simulation of a magnetopause surface eigenmode. These show monochromatic oscillatory field-aligned currents (FACs), due to both the surface mode and its non-resonant Alfvén coupling, are present throughout the magnetosphere. The currents peak in amplitude at the equatorward edge of the magnetopause boundary layer, not the open-closed boundary as previously thought. They also exhibit slow poleward phase motion rather than being purely evanescent. We suggest the upward FAC perturbations may result in periodic auroral brightenings. In the ionosphere, convection vortices circulate the poleward moving FAC structures. Finally, surface mode signals are predicted in the ground magnetic field, with ionospheric Hall currents rotating perturbations by approximately (but not exactly) 90° compared to the magnetosphere. Thus typical dayside magnetopause surface modes should be strongest in the East-West ground magnetic field component. Overall, all ground-based signatures of the magnetopause surface mode are predicted to have the same frequency across L-shells, amplitudes that maximize near the magnetopause's equatorward edge, and larger latitudinal scales than for field line resonance. Implications in terms of ionospheric Joule heating and geomagnetically induced currents are discussed.
Date Issued
2023-03
Date Acceptance
2023-02-16
Citation
Journal of Geophysical Research: Space Physics, 2023, 128 (3), pp.1-25
ISSN
2169-9380
Publisher
American Geophysical Union
Start Page
1
End Page
25
Journal / Book Title
Journal of Geophysical Research: Space Physics
Volume
128
Issue
3
Copyright Statement
©2023. The Authors.
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.
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
Sponsor
Natural Environment Research Council (NERC)
Science and Technology Facilities Council (STFC)
Engineering & Physical Science Research Council (EPSRC)
UKRI
Natural Environment Research Council (NERC)
Identifier
https://agupubs.onlinelibrary.wiley.com/doi/10.1029/2022JA031081
Grant Number
NE/P017142/1
ST/S000364/1
EP/T01735X/1
EP/T01735X/1
NE/V003070/1
Subjects
physics.space-ph
physics.space-ph
astro-ph.EP
physics.plasm-ph
0201 Astronomical and Space Sciences
0401 Atmospheric Sciences
Publication Status
Published
Article Number
e2022JA031081
Date Publish Online
2023-02-24