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Geophys. J. Int. (2011) 186, 118136 doi: 10.1111/j.1365-246X.2011.05037.x GJIGeomagnetism,rockmagnetismandpalaeomagnetism

Summary: Geophys. J. Int. (2011) 186, 118­136 doi: 10.1111/j.1365-246X.2011.05037.x
Inference on core surface flow from observations and 3-D
dynamo modelling
Alexandre Fournier, Julien Aubert and Erwan Th´ebault
Institut de Physique du Globe de Paris, Sorbonne Paris Cit´e, Universit´e Paris Diderot, INSU/CNRS (UMR 7154), F-75005 Paris, France.
E-mail: fournier@ipgp.fr
Accepted 2011 April 1. Received 2011 April 1; in original form 2010 September 15
We show how a 3-D, self-consistent numerical model of the geodynamo can be used as the
subjective prior information for the determination of Earth's core surface flows from the
geomagnetic field and its secular variation. This is achieved by estimating those parts of the
numerical model state vector hidden from the observations, through a standard Kalman filtering
(or stochastic inverse) procedure, where the Kalman gain matrix is based on the multivariate
statistics of the geodynamo model. To allow for a direct comparison with observations, the field
variables entering these statistics are scaled following two of the scaling laws that have recently
come to the fore in numerical dynamo modelling, which express the dependency of the secular
variation timescale and the magnetic energy density on their respective control parameters.
We perform test experiments with noisy synthetic data, showing good to excellent recovery of
the hidden parts of the state vector. A geomagnetic field model parent to a candidate model to


Source: Aubert, Julien - Institut de Physique du Globe de Paris
Fournier, Alexandre - Equipe de Geomagnetisme, Institut de Physique du Globe de Paris


Collections: Geosciences