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Maximum entropy regularization of the geomagnetic core field inverse problem

Jackson, Andrew ; Constable, Catherine ; Gillet, Nicolas

In: Geophysical Journal International, 2007, vol. 171, no. 3, p. 995-1004

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    Titre
    • Maximum entropy regularization of the geomagnetic core field inverse problem
    Auteur
    • Jackson, Andrew. Institut für Geophysik, ETH Zürich, CH-8093, Switzerland
    • Constable, Catherine. IGPP, Scripps Inst. of Oceanography, La Jolla 92093 CA, USA
    • Gillet, Nicolas. School of Earth and Environment, University of Leeds, Leeds LS2 9JT, UK. E-mail: earng@earth.leeds.ac.uk
    Type de document
    • Postprint
    Identifiant OAI-PMH
    • oai:doc.rero.ch:290353
    Summary
    The maximum entropy technique is an accepted method of image reconstruction when the image is made up of pixels of unknown positive intensity (e.g. a grey-scale image). The problem of reconstructing the magnetic field at the core-mantle boundary from surface data is a problem where the target image, the value of the radial field Br, can be of either sign. We adopt a known extension of the usual maximum entropy method that can be applied to images consisting of pixels of unconstrained sign. We find that we are able to construct images which have high dynamic ranges, but which still have very simple structure. In the spherical harmonic domain they have smoothly decreasing power spectra. It is also noteworthy that these models have far less complex null flux curve topology (lines on which the radial field vanishes) than do models which are quadratically regularized. Problems such as the one addressed are ubiquitous in geophysics, and it is suggested that the applications of the method could be much more widespread than is currently the case