Physics
Scientific paper
May 2011
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2011georl..3810309s&link_type=abstract
Geophysical Research Letters, Volume 38, Issue 10, CiteID L10309
Physics
1
Geodesy And Gravity: Earth'S Interior: Dynamics (1507, 7207, 7208, 8115, 8120), Geodesy And Gravity: Earth Rotation Variations, Geomagnetism And Paleomagnetism: Core Processes (1213, 8115), Geomagnetism And Paleomagnetism: Time Variations: Secular And Longer
Scientific paper
Quasi-geostrophic (QG) flows are a recently developed and very promising paradigm for modeling decadal secular variation (SV). Here we examine the effects of allowing anisotropy and departures of the flow from quasigeostrophy. We perform dedicated numerical experiments of the flow dynamics and magnetic induction inside the Earth's liquid core at time scales characteristic of secular variation of the geomagnetic field. Obtained results motivate new flow inversion regularization featuring an equatorially anti-symmetric component superimposed to quasi-geostrophic columns, and stronger latitudinal than longitudinal flow gradients. Applying these constraints allows to explain the observed SV for the whole period 1840-2010, and most significantly, provides a clearly improvement in prediction for decadal length-of-day variations for the period 1980-2000. Furthermore, the trace of the inner-core appears clearly without any assumption for the 1997-2010 period covered by satellite geomagnetic data. Our results support QG being the appropriate description of the force balance within the core on decadal time scales and large spatial scales.
Pais M. A.
Schaeffer Nathanaël
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