A review of the theory of 3‐D Alfvén (field line) resonances

Elsden, T. , Wright, A. and Degeling, A. (2022) A review of the theory of 3‐D Alfvén (field line) resonances. Frontiers in Astronomy and Space Sciences, 9, 917817. (doi: 10.3389/fspas.2022.917817)

Abstract

This review article aims to summarise recent developments in Alfvén resonance theory, with a focus on applications to magnetospheric ultra-low frequency (ULF) waves, though many of the ideas are relevant for applications in other fields as well. The key aspect we treat is how Alfvén resonance manifests in a fully 3-D varying medium. The prerequisite ideas are developed in a reasonably comprehensive introduction, which would be a good starting point for any interested reader looking to gain an understanding of the Alfvén resonance process, as well as where to find associated reading. The main part of the review is split into three sections. We firstly consider results from numerical simulations of relatively simple magnetic field geometries, such as 2-D and 3-D dipoles, to develop the fundamental properties of 3-D Alfvén resonances. Secondly, we review previous simulations in more general magnetic field geometries, reconciling these results with those from the simpler dipole cases. Thirdly, in light of these numerical results, we review theoretical studies using various analytical methods to find approximate solutions to the pertinent magnetohydrodynamic (MHD) equations. The review is concluded with a discussion of these different approaches, as well as linking these ideas to their importance for observations. Finally, we discuss potential future developments in this research area.

• Item Type: Articles
• Additional Information: Funding: TE is funded by a Leverhulme Trust Early Career Fellowship (ECF-2019–155) and the University of Glasgow. AW was partially funded by the Science and Technology Facilities Council (STFC) grant (ST/N000609/1). AD is supported by the National Natural Science Foundation of China (41,774,172).
• Keywords: Astronomy and Space Sciences, field line resonance, ULF waves, magnetosphere, alfvén resonance, MHD waves, numerical modelling, fast-Alfven wave coupling
• Status: Published
• Refereed: Yes
• Glasgow Author(s) Enlighten ID: Elsden, Dr Thomas
• Authors: Elsden, T., Wright, A., and Degeling, A.
• College/School: College of Science and Engineering > School of Mathematics and Statistics
• Journal Name: Frontiers in Astronomy and Space Sciences
• Publisher: Frontiers Media
• ISSN: 2296-987X
• ISSN (Online): 2296-987X
• Published Online: 13 September 2022
• Copyright Holders: Copyright © 2022 Elsden, Wright and Degeling
• First Published: First published in Frontiers in Astronomy and Space Sciences 9: 917817
• Publisher Policy: Reproduced under a Creative Commons License