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dc.contributor.authorElsden, T.
dc.contributor.authorWright, A. N.
dc.identifier.citationElsden , T & Wright , A N 2018 , ' The broadband excitation of 3D Alfvén resonances in a MHD waveguide ' , Journal of Geophysical Research: Space Physics , vol. 123 , no. 1 , pp. 530-547 .
dc.identifier.otherPURE: 252115432
dc.identifier.otherPURE UUID: 9971cbfa-cc7c-42f1-92b9-70e090b01220
dc.identifier.otherBibtex: urn:1d1ac47b3af52f790b3041f0123b718f
dc.identifier.otherScopus: 85041080327
dc.identifier.otherORCID: /0000-0002-9877-1457/work/58055390
dc.identifier.otherORCID: /0000-0002-1910-2010/work/60196735
dc.identifier.otherWOS: 000425637600039
dc.descriptionT. Elsden and A. N. Wright were funded by The Leverhulme Trust through Research Grant RPG-2016-071. A. N. Wright was also funded by STFC through Consolidated Grant ST/N000609/1. Data from simulation results are available on Figshare:
dc.description.abstractThis paper considers the resonant coupling of fast and Alfvén magnetohydrodynamic (MHD) waves. We perform numerical simulations of the time-dependent excitation of Alfvén resonances in a dipole magnetic field, with nonuniform density providing a 3-D equilibrium. Wright and Elsden (2016) showed that in such a system where the poloidal and toroidal Alfvén eigenfrequencies are different, the resonance can have an intermediate polarization, between poloidal and toroidal. We extend this work by driving the system with a broadband rather than monochromatic source. Further, we investigate the effect of azimuthal inhomogeneity on the resonance path. It is found that when exposed to a broadband driver, the dominant frequencies are the fast waveguide eigenfrequencies, which act as the drivers of Alfvén resonances. We demonstrate how resonances can still form efficiently with significant amplitudes, even when forced by the medium to have a far from toroidal polarization. Indeed, larger-amplitude resonances can be generated with an intermediate polarization, rather than purely toroidal, as a result of larger gradients in the magnetic pressure formed by the azimuthal inhomogeneity. Importantly, the resonance structure is shown to be independent of the different forms of driving, meaning their locations and orientations may be used to infer properties of the equilibrium. However, the amplitude of the FLRs are sensitive to the spatial structure and frequency spectrum of the magnetopause driving. These results have implications for the structure of field line resonances (FLRs) in Earth's magnetosphere, although the focus of this paper is on the underlying physics involved.
dc.relation.ispartofJournal of Geophysical Research: Space Physicsen
dc.rights©2018. American Geophysical Union. This work has been made available online in accordance with the publisher’s policies. This is the author created, accepted version manuscript following peer review and may differ slightly from the final published version. The final published version of this work is available at
dc.subjectField line resonanceen
dc.subjectMHD wavesen
dc.subjectAlfven resonanceen
dc.subjectMode couplingen
dc.subjectEarth's magnetosphereen
dc.subjectQB Astronomyen
dc.subjectQC Physicsen
dc.titleThe broadband excitation of 3D Alfvén resonances in a MHD waveguideen
dc.typeJournal articleen
dc.description.versionPublisher PDFen
dc.contributor.institutionUniversity of St Andrews.Applied Mathematicsen
dc.description.statusPeer revieweden

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