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Convection in the Earth's core driven by lateral variations in the core-mantle boundary heat flux

Gibbons, S.J. and Gubbins, D. (2000) Convection in the Earth's core driven by lateral variations in the core-mantle boundary heat flux. Geophysical Journal International, 142 (2). pp. 631-642. ISSN 0956-540X

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Abstract

Moving core fluid maintains an isothermal core-mantle boundary (CMB), so lateral variations in the CMB heat flow result from mantle convection. Such variations will drive thermal winds, even if the top of the core is stably stratified. These flows may contribute to the magnetic secular variation and are investigated here using a simple, non-magnetic numerical model of the core. The results depend on the equatorial symmetry of the boundary heat flux variation. Large-scale equatorially symmetric (ES) heat flux variations at the outer surface of a rapidly rotating spherical shell drive deeply penetrating flows that are strongly suppressed in stratified fluid. Smaller-scale ES heat flux variations drive flows less dominated by rotation and so less inhibited by stratification. Equatorially anti-symmetric flux variations drive flows an order of magnitude less energetic than those driven by ES patterns but, due to the nature of the Coriolis force, are less suppressed by stratification. The response of the rotating core fluid to a general CMB heat flow pattern will then depend strongly on the subadiabatic temperature profile. Imposing a lateral heat flux variation linearly related to a model of seismic tomography in the lowermost mantle drives flow in a density stratified fluid that reproduces some features found in flows inverted from geomagnetic data.

Item Type: Article
Copyright, Publisher and Additional Information: © 2000 RAS. This is an electronic version of an article published in Geophysical Journal International: complete citation information for the final version of the paper, as published in the print edition of Geophysical Journal International, is available on the Blackwell Synergy online delivery service, accessible via the journal's website at http://www.blackwellpublishing.com/journal.asp?ref=0956-540X or www.blackwell-synergy.com
Keywords: convection, core-mantle boundary, geomagnetism, heat flux, stratification,symmetries.
Institution: The University of Leeds
Academic Units: The University of Leeds > Faculty of Environment (Leeds) > School of Earth and Environment (Leeds)
Depositing User: Sherpa Assistant
Date Deposited: 04 May 2005
Last Modified: 05 Jun 2014 10:45
Published Version: http://www.blackwell-synergy.com/
Status: Published
Refereed: Yes
Identification Number: 10.1046/j.1365-246x.2000.00192.x
URI: http://eprints.whiterose.ac.uk/id/eprint/417

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