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Intense equatorial flux spots on the surface of the Earth's core

Nature volume 424, pages 760–763 (2003)Cite this article

Abstract

A large number of high-accuracy vector measurements of the Earth's magnetic field have recently become available from the satellite Oersted, complementing previous vector data from the satellite Magsat, which operated in 1979/80. These data can be used to infer the morphology of the magnetic field at the surface of the fluid core1, ∼2,900 km below the Earth's surface. Here I apply a new methodology to these data to calculate maps of the magnetic field at the core surface which show intense flux spots in equatorial regions. The intensity of these features is unusually large—some have intensities comparable to high-latitude flux patches near the poles, previously identified as the major component of the dynamo field2. The tendency for pairing of some of these spots to the north and south of the geographical equator suggests they might be associated with the tops of equatorially symmetric columnar structures in the fluid, or their antisymmetric equivalents. The drift of the equatorial features may represent material flow or could represent wave motion; discrimination of these two effects based on future data could provide new information on the strength of the hidden toroidal magnetic field of the Earth.

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Figure 1: Comparison of the radial magnetic field for epochs 1980 and 2000 on Aitoff equal-area projection.
Figure 2
Figure 3: The palaeomagnetic time-average radial magnetic field for the last 2.5 Myr (ref.17), derived by a conventional quadratic regularization method, showing the presence of an equatorial flux spot under the Indian Ocean.

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Acknowledgements

The provision of high-quality Oersted data is due to the efforts of the Oersted Project team, for which I am grateful. I thank C. Constable and R. Parker for their hospitality, discussions and sharing of software, and C. Finlay for comments.

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  1. School of Earth Sciences, University of Leeds, LS2 9JT, Leeds, UK

    Andrew Jackson

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Correspondence to Andrew Jackson.

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Jackson, A. Intense equatorial flux spots on the surface of the Earth's core. Nature 424, 760–763 (2003). https://doi.org/10.1038/nature01879

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