Rapidly changing flows in the Earth’s core

Abstract

A large part of the Earth’s magnetic field is generated by fluid motion in the molten outer core1. As a result of continuous satellite measurements since 1999, the core magnetic field and its recent variations can now be described with a high resolution in space and time2. These data have recently been used to investigate small-scale core flow3,4, but no advantage has yet been taken of the improved temporal resolution, partly because the filtering effect of the electrically conducting mantle was assumed to mask short-period magnetic variations5. Here we show that changes in the magnetic field occurring over only a few months, indicative of fluid flow at the top of the core, can in fact be resolved. Using nine years of magnetic field data obtained by satellites as well as Earth-based observatories, we determine the temporal changes in the core magnetic field and flow in the core. We find that the core flow is spatially localized and involves rapid variations over a few months, with surprisingly large local accelerations. Our results suggest that short-term fluctuations of the core magnetic field are robust features of rapid core dynamics and should be considered in the development of future numerical models of the geodynamo.

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Figure 1: Observed and modelled secular variation.
Figure 2: Map of annual difference of the second time derivative of the vertical component for epoch 2003.5.
Figure 3: Map of annual difference of the second time derivative of the vertical component for epoch 2004.7.
Figure 4: Observed and modelled LOD variations.

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Acknowledgements

We thank Chris Finlay and Dominique Jault for comments and discussion.

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Correspondence to Nils Olsen.

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Supplementary figures S1-S2 and tables S1-S2 (PDF 141 kb)

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Olsen, N., Mandea, M. Rapidly changing flows in the Earth’s core. Nature Geosci 1, 390–394 (2008). https://doi.org/10.1038/ngeo203

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