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On the strength of electric currents and zonal magnetic fields at the top of the Earth's core: Methodology and preliminary estimates |
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| Authors: | Edward R Benton Lorant A Muth |
| Institution: | a Department of Astro-Geophysics, University of Colorado, Boulder, CO 80309, U.S.A. b Department of Physics and Astrophysics, University of Colorado, Boulder, CO 80309, U.S.A. |
| Abstract: | A new method is described for estimating: (a) the meridional electric current density, jθ, (b) the vertical growth rate of the zonal magnetic field, ?Bφ/?r, or its scale-height, Bφ/?Bφ/?r) and (c) the vertical growth rate of the vertical current density, ?jr/?r, at a few isolated points on the top surface of the Earth's core from observations of the internal geomagnetic field at the Earth's surface. The theoretical technique rests on combining unaccelerated, gravitationally-driven Boussinesq fluid dynamics of the core with frozen-flux electromagnetism, the mantle being treated as a spherically symmetric insulator. Insertion into this theory of main field models for epochs 1965, 1975 leads to preliminary values for these quantities of magnitude: (a) jθ |
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1 A/m2, (b) ?Bφ/?r