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Gyre-driven decay of the Earth’s magnetic dipole

Author

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  • Christopher C. Finlay

    (DTU Space, Technical University of Denmark)

  • Julien Aubert

    (Dynamique des Fluides Géologiques, Institut de Physique du Globe de Paris)

  • Nicolas Gillet

    (ISTerre, Université Grenoble 1, CNRS)

Abstract

Direct observations indicate that the magnitude of the Earth’s magnetic axial dipole has decreased over the past 175 years; it is now 9% weaker than it was in 1840. Here we show how the rate of dipole decay may be controlled by a planetary-scale gyre in the liquid metal outer core. The gyre’s meridional limbs on average transport normal polarity magnetic flux equatorward and reverse polarity flux poleward. Asymmetry in the geomagnetic field, due to the South Atlantic Anomaly, is essential to the proposed mechanism. We find that meridional flux advection accounts for the majority of the dipole decay since 1840, especially during times of rapid decline, with magnetic diffusion making an almost steady contribution generally of smaller magnitude. Based on the morphology of the present field, and the persistent nature of the gyre, the current episode of dipole decay looks set to continue, at least for the next few decades.

Suggested Citation

  • Christopher C. Finlay & Julien Aubert & Nicolas Gillet, 2016. "Gyre-driven decay of the Earth’s magnetic dipole," Nature Communications, Nature, vol. 7(1), pages 1-8, April.
    • Handle: RePEc:nat:natcom:v:7:y:2016:i:1:d:10.1038_ncomms10422
    DOI: 10.1038/ncomms10422
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