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Constraints on the Lower Mantle Electrical Conductivity: Limitations on Backus Mantle Filter Theory and the Inverse Problem
- Publisher: European Association of Geoscientists & Engineers
- Source: Conference Proceedings, 12th International Congress of the Brazilian Geophysical Society, Aug 2011, cp-264-00129
Abstract
In this paper we constrain the electrical conductivity of the lower mantle is by using geomagnetic jerks that are abrupt changes in the secular variation generated in the core. By appling Backus’ (1983) mantle filter theory it is possible to show that a simple 1D mantle conductivity model is able to generate differential delays. However, Backus’s (1983) theory considers a low frequency approximation of the transfer function that presents some limitations. We also calculate of the Impulse Response Function (IRF) by a modified version of Velm˙ sky´ and Martinec’s (2005) code, using a direct time-integration of the EM induction equation. The inverse problem was solved, by exhaustive search. The misfit values for all simulations, favour a low conductivity of the lower mantle of about 1 S/m.