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Z .Physics of the Earth and Planetary Interiors 117 2000 111121 www.elsevier.comrlocaterpepi

Summary: Z .Physics of the Earth and Planetary Interiors 117 2000 111­121
Control of inner core rotation by electromagnetic, gravitational
and mechanical torques
Jonathan Aurnou )
, Peter Olson
Department of Earth and Planetary Sciences, Johns Hopkins UniÕersity, Baltimore, MD 21218 USA
Received 28 October 1998; accepted 20 April 1999
We compute the polar rotation of the Earth's inner core in response to the combined effects of electromagnetic,
gravitational and mechanical torques. We obtain electromagnetic torques between 1018
and 1020
Nm, compared to
19 21 wgravitational torques between 10 and 10 Nm estimated by Xu et al. Xu, S., Crossley D., Szeto, A.M.K., 1999.
Variations in length of day and inner core differential rotation from gravitational coupling. Phys. Earth Planet. Inter., 116,
x w95­110 and Buffett Buffett, B.A., 1996b. A mechanism for decade fluctuations in the length of day. Geophys. Res. Lett.,
x 15
23, 3803­3806. , respectively. We obtain mechanical torques on the order of 10 Nm. Gravitationally dominated cases
produce inner core oscillations with periods between 1 and 10 years. In electromagnetically dominated cases, the inner core
rotates close to the imposed rotation rate of the outer core fluid. Modulations in the rotation rate are produced as the inner


Source: Aurnou, Jonathan - Department of Earth and Space Sciences, University of California at Los Angeles


Collections: Geosciences