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Earth Planets Space, 60, 845854, 2008 A simple model for mantle-driven flow at the top of Earth's core
 

Summary: Earth Planets Space, 60, 845­854, 2008
A simple model for mantle-driven flow at the top of Earth's core
Hagay Amit1
, Julien Aubert2
, Gauthier Hulot1
, and Peter Olson3
1Equipe de G´eomagn´etisme, Institut de Physique du Globe de Paris (Institut de Recherche associ´e au CNRS et `a l'Universit´e Paris 7),
4 Place Jussieu, 75252 Paris Cedex 05, France
2Equipe de Dynamique des Syst`emes G´eologiques, Institut de Physique du Globe de Paris
3Department of Earth and Planetary Sciences, Johns Hopkins University, Baltimore, MD 21218, USA
(Received November 15, 2007; Revised April 7, 2008; Accepted April 26, 2008; Online published September 8, 2008)
We derive a model for the steady fluid flow at the top of Earth's core driven by thermal coupling with
the heterogeneous lower mantle. The model uses a thermal wind balance for the core flow, and assumes a
proportionality between the horizontal density gradients at the top of the core and horizontal gradients in seismic
shear velocity in the lowermost mantle. It also assumes a proportionality between the core fluid velocity and
its radial shear. This last assumption is validated by comparison with numerical models of mantle-driven core
flow, including self-sustaining dynamo (supercritical) models and non-magnetic convection (subcritical) models.
The numerical dynamo models show that thermal winds with correlated velocity and radial shear dominate the
boundary-driven large-scale flow at the top of the core. We then compare the thermal wind flow predicted by
mantle heterogeneity with the 150 year time-average flow obtained from inverting the historical geomagnetic

  

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

 

Collections: Geosciences