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Published September 1990 | Published
Journal Article Open

Modeling core fluid motions and the drift of magnetic field patterns at the CMB by use of topography obtained by seismic inversion

  • 1. ROR icon California Institute of Technology


The thermal wind equations, in which the Coriolis force is balanced by pressure gradients and horizontal density gradients rather than by Lorentz forces, are used to describe patterns of magnetic field drift associated with core fluid motions near the core-mantle boundary (CMB). The advection of magnetic field may be due in part to the flow driven by such horizontal temperature gradients, just as East-West air flow is driven by North-South temperature gradients in the Earth's atmosphere. It is argued that this flow may be concentrated in a shell near the CMB, and the horizontal temperature gradients are expected to be directly proportional to horizontal gradients in CMB topography, the lowest harmonics of which are approximately constrained in seismology. Part of the zonal drift is then associated with the 1=2, m=0 harmonic of CMB topography, and anticyclones are attached to topographic highs (thermal highs). Comparison of our derived flow pattern with those determined purely by magnetic field observations provides tentative support for our model.

Additional Information

© 1990 by the American Geophysical Union. Received: May 2, 1990; accepted June 18, 1990. We thank Jeremy Bloxham for Discussions and Rob Clayton for the use of his computer graphics programs. This work is supported in part by NSF grant EAR-8816268. Contribution number 4872 of the Division of Geological and Planetary Sciences.

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