Dynamos driven by weak thermal convection and heterogeneous outer boundary heat flux

Sahoo, Swarandeep and Sreenivasan, Binod and Amit, Hagay (2016) Dynamos driven by weak thermal convection and heterogeneous outer boundary heat flux. In: PHYSICS OF THE EARTH AND PLANETARY INTERIORS, 250 . pp. 35-45.

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Abstract

We use numerical dynamo models with heterogeneous core-mantle boundary (CMB) heat flux to show that lower mantle lateral thermal variability may help support a dynamo under weak thermal convection. In our reference models with homogeneous CMB heat flux, convection is either marginally supercritical or absent, always below the threshold for dynamo onset. We find that lateral CMB heat flux variations organize the flow in the core into patterns that favour the growth of an early magnetic field. Heat flux patterns symmetric about the equator produce non-reversing magnetic fields, whereas anti-symmetric patterns produce polarity reversals. Our results may explain the existence of the geodynamo prior to inner core nucleation under a tight energy budget. Furthermore, in order to sustain a strong geomagnetic field, the lower mantle thermal distribution was likely dominantly symmetric about the equator. (C) 2015 Elsevier B.V. All rights reserved.

Item Type:	Journal Article
Publication:	PHYSICS OF THE EARTH AND PLANETARY INTERIORS
Publisher:	ELSEVIER SCIENCE BV
Additional Information:	Copy right for this article belongs to the ELSEVIER SCIENCE BV, PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS
Keywords:	Geodynamo; Early Earth; Geomagnetic field; Core-mantle interaction; Helicity generation
Department/Centre:	Division of Mechanical Sciences > Centre for Earth Sciences
Date Deposited:	04 Mar 2016 07:41
Last Modified:	04 Mar 2016 07:41
URI:	http://eprints.iisc.ac.in/id/eprint/53327

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