Hardy, CM, Livermore, PW orcid.org/0000-0001-7591-6716 and Niesen, J orcid.org/0000-0002-6693-3810 (2022) The inherent instability of axisymmetric magnetostrophic dynamo models. Geophysical and Astrophysical Fluid Dynamics, 116 (5-6). pp. 499-520. ISSN 0309-1929
Abstract
Recent studies have demonstrated the possibility of constructing magnetostrophic dynamo models, which describe the slowly evolving background state of Earth's magnetic field when inertia and viscosity are negligible. Here we explore the properties of steady, stable magnetostrophic states as a leading order approximation to the slow dynamics within Earth's core. For the case of an axisymmetric magnetostrophic system driven by a prescribed α-effect, we confirmed the existence of four known steady states: ±Bd, ±Bq, where Bd is purely dipolar and Bq is purely quadrupolar. Importantly, here we show that in all but the most weakly driven cases, an initial magnetic field that is not purely dipolar or quadrapolar never converges to these states. Despite this instability, we also show that there are a plethora of instantaneous solutions that are quasi-steady, but nevertheless unstable. If the dynamics in Earth's core are reasonably modelled by a strongly driven α-effect, this work suggests that the background state can never be steady. We discuss the difficulties in comparing our magnetostrophic models with geomagnetic timeseries.
Metadata
Item Type: | Article |
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Authors/Creators: |
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Copyright, Publisher and Additional Information: | © 2022 The Author(s). Published by Informa UK Limited, trading as Taylor & Francis GroupThis is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/4.0/), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properlycited. |
Keywords: | Taylor’s constraint; geodynamo; Earth’s core; magnetostrophic |
Dates: |
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Institution: | The University of Leeds |
Academic Units: | The University of Leeds > Faculty of Engineering & Physical Sciences (Leeds) > School of Mathematics (Leeds) > Applied Mathematics (Leeds) The University of Leeds > Faculty of Environment (Leeds) > School of Earth and Environment (Leeds) > Inst of Geophysics and Tectonics (IGT) (Leeds) |
Funding Information: | Funder Grant number NERC (Natural Environment Research Council) NE/G014043/1 |
Depositing User: | Symplectic Publications |
Date Deposited: | 13 Dec 2022 17:10 |
Last Modified: | 10 Jan 2023 12:52 |
Status: | Published |
Publisher: | Taylor & Francis |
Identification Number: | 10.1080/03091929.2022.2148666 |
Open Archives Initiative ID (OAI ID): | oai:eprints.whiterose.ac.uk:193947 |
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