期刊
PHYSICS OF THE EARTH AND PLANETARY INTERIORS
卷 250, 期 -, 页码 35-45出版社
ELSEVIER SCIENCE BV
DOI: 10.1016/j.pepi.2015.11.003
关键词
Geodynamo; Early Earth; Geomagnetic field; Core-mantle interaction; Helicity generation
资金
- Department of Science and Technology (Government of India)
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.
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