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The timedependence of intense archeomagnetic flux patches Hagay Amit,1

Summary: The timedependence of intense archeomagnetic flux patches
Hagay Amit,1
Monika Korte,2
Julien Aubert,3
Catherine Constable,4
and Gauthier Hulot5
Received 19 May 2011; revised 21 September 2011; accepted 6 October 2011; published 14 December 2011.
[1] The longterm temporal behavior of intense geomagnetic flux patches at the
coremantle boundary and the relation with lower mantle lateral heterogeneity are under
debate. We apply an algorithm to detect centers of intense flux patches and track their
timeevolution in a recent archeomagnetic field model in order to study the kinematics of
such intense magnetic flux patches on millennial timescale. We find that most intense flux
patches appear near the edge of the tangent cylinder. Quasistationary periods with small
oscillations of patches occur more than drifts. Detailed comparison of the archeomagnetic
patches' behavior with that seen in numerical dynamos with tomographic heat flux boundary
conditions suggests that coremantle thermal coupling could be the cause of a statistical
preference for some longitudes on the long term, which does not exclude significant time
spent away from the preferred longitudes. This could explain the roughly coincident
locations of highlatitude patches in the historical geomagnetic field with that of the
timeaverage paleomagnetic field together with the much weaker patches intensity in the


Source: Aubert, Julien - Institut de Physique du Globe de Paris


Collections: Geosciences