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Science 27 June 2003:
Vol. 300. no. 5628, pp. 2084 - 2086
DOI: 10.1126/science.1083324
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Reports

Equatorially Dominated Magnetic Field Change at the Surface of Earth's Core

Christopher C. Finlay* and Andrew Jackson

Slow temporal variations in Earth's magnetic field originate in the liquid outer core. We analyzed the evolution of nonaxisymmetric magnetic flux at the core surface over the past 400 years. We found that the most robust feature is westward motion at 17 kilometers per year, in a belt concentrated around the equator beneath the Atlantic hemisphere. Surprisingly, this motion is dominated by a single wavenumber and persists throughout the observation period. This phenomenon could be produced by an equatorial jet of core fluid, by hydromagnetic wave propagation, or by a combination of both. Discrimination between these mechanisms would provide useful constraints on the dynamics of Earth's core.

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

* To whom correspondence should be addressed. E-mail: c.finlay{at}earth.leeds.ac.uk

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