The flow at the core-mantle boundary: symmetry properties

Abstract

It is shown that a geostrophic flow with a plane reflexion symmetry about the equatorial plane and a simple symmetry about the Earth's centre for the non-zonal component accounts for the 1980 geomagnetic secular variation (S.V.) although the number of parameters of the flow is reduced by a factor eight (from the number necessary when no assumption is made); the relative misfit between the predicted and the observed S.V. is of the same order as those existing between various 1980 S.V. models. The so-obtained flow exhibits a rather simple configuration. A means of downward continuing the flow into the body of the core is suggested which leads to some integral constraints on the density heterogeneity in the core. -from Authors