Geomagnetic effects of the Earth's ellipticity |
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| Authors: | Andrew Jackson Denis Winch & Vincent Lesur |
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| Institution: | Department of Earth Sciences, Leeds University, Leeds, LS2 9JT, UK. E-mail:;, Department of Applied Maths, University of Sydney, Sydney, NSW 2006, Australia |
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| Abstract: | We analyse the external field generated by a uniform distribution of magnetic susceptibility contained in an oblate spheroidal shell when it is magnetized by an internal magnetic field of arbitrary complexity. The situation is more relevant to the Earth than that of a spherical shell considered by Runcorn (1975a ) (in the context of lunar magnetism), because of the larger flattening of the Earth than that of the Moon. We find that, to first order in the susceptibility, each internal harmonic in a spheroidal harmonic expansion of the magnetic potential generates just one non-vanishing external field coefficient, unlike in the spherical case when all harmonics vanish identically. The field generated is proportional to the susceptibility, thickness of the shell and square of the Earth's eccentricity, and hence it appears that this field amplification mechanism will be very ineffective for the Earth. |
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| Keywords: | Earth's ellipticity geomagnetism |
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