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Russian Geology and Geophysics

2003 year, number 7

LARGE-SCALE CONVECTION IN CELLS SURROUNDING THE EARTH'S AXIS: A POSSIBLE GEODYNAMO MECHANISM

V.V. Botvinovsky
Institute of Geophysics, Siberian Branch of the RAS, 3 prosp. Akad. Koptyuga, Novosibirsk, 630090, Russia
Keywords: Geomagnetic field, hydromagnetic dynamo, convection, jerk, westward drift, plume
Pages: 690-696

Abstract

Excitation of the Earth's magnetic field is explained in terms of the common magnetohydrodynamic (MHD) mechanism in the conducting fluid core. The proposed scheme of motion implies hydromagnetic induction of azimuthal currents, according to the left-hand rule, and their distribution is the same as that obtained by simulating the source of the axisymmetrical part of the geomagnetic field. The fluid core material, with conductivity typical ofimpurity-bearing iron, was estimated to flow at 5 x 10-6 m/s. The scheme is consistent with the outstripping rotation of the inner core and the westward drift of small-scale field heterogeneities. This approach accounts for jerks and their relationship with irregularity in the Earth's rotation. Reversals and excursions of magnetic poles may be caused by changes in correlation between the meridional and azimuthal flows or by plumes in the fluid core.