Plumley, M, Calkins, MA, Julien, K et al. (1 more author) (2018) Self-consistent single mode investigations of the quasi-geostrophic convection-driven dynamo model. Journal of Plasma Physics, 84 (4). ARTN 735840406. ISSN 0022-3778
Abstract
The quasi-geostrophic dynamo model (QGDM) is a multiscale, fully nonlinear Cartesian dynamo model that is valid in the asymptotic limit of low Rossby number. In the additional limit of small magnetic Prandtl number investigated here, the QGDM is a self-consistent, asymptotically exact form of an large-scale dynamo. This article explores methods for simulating the multiscale QGDM and investigates how convection is altered by the magnetic field in the planetary regime of small Rossby number and small magnetic Prandtl number. At present, this combination is beyond the reach of direct numerical simulations. We use a simplified class of solutions whose horizontal structure is restricted to a periodic hexagonal lattice characterized by a single horizontal wavenumber (single mode). In contrast with previous kinematic investigations of the QGDM, the Lorentz force is included to study saturated, self-consistent dynamos. Two methodologies are used to assess handling of the multiple time scales of the QGDM: a stiff, common-in-time approach where all time scales are converted to a single time variable and a heterogeneous multiscale modelling approach employing fast time averaging on the Reynolds, magnetic and buoyancy eddy fluxes that feed back onto the slow scales. These strategies produce consistent results and each illustrates self-similar dynamics as the time-averaging window is increased. The properties of the convection are significantly altered by the dynamo-generated magnetic field. All solutions show a decrease in the overall heat transfer efficiency as compared to non-magnetic convection, suggesting that a change in length scale or flow planform plays a critical role in the enhanced heat transfer efficiency observed in previous dynamo studies. All dynamo solutions show a trend of increasing ohmic dissipation relative to viscous dissipation as the buoyancy forcing is increased.
Metadata
Item Type: | Article |
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Authors/Creators: |
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Copyright, Publisher and Additional Information: | © Cambridge University Press 2018. This article has been published in a revised form in Journal of Plasma Physics https://doi.org/10.1017/S0022377818000831. This version is free to view and download for private research and study only. Not for re-distribution, re-sale or use in derivative works. |
Keywords: | plasma dynamics; plasma flows |
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) |
Depositing User: | Symplectic Publications |
Date Deposited: | 16 Jul 2018 13:58 |
Last Modified: | 13 Feb 2019 01:39 |
Status: | Published |
Publisher: | Cambridge University Press |
Identification Number: | 10.1017/S0022377818000831 |
Open Archives Initiative ID (OAI ID): | oai:eprints.whiterose.ac.uk:133297 |