ELECTRIC-FIELDS DERIVED FROM THE EARTHS MAGNETIC-FIELD AND THEIR APPLICATION TO FLUID MOTION IN THE OUTER CORE

Several years ago I discovered an intriguing spatial correlation betwe en plate motions and variations in the strength of the geomagnetic fie ld with the major lithospheric plates tending to move from areas where the magnetic field is diminished to where it is enhanced (GOODACRE, 1 987). One implication of this visual correlation is that there is a li nk between the pattern of fluid motion in the Earth's outer core and t he convection of material in the mantle. In order to estimate the moti on of fluid in the outermost portion of the core, we require a knowled ge of not only the magnetic vector potential, A, and its time variatio n, but also the scalar electrostatic potential, Psi. Under the assumpt ion that there is no large, time-varying toroidal magnetic field in th e Earth's core I have calculated smooth representations of the induced electric field intensity, -partial derivative A/partial derivative t, the electrostatic field intensity, -del Psi, and the motional electri c field intensity, v x B, needed to generate electric currents which r eproduce the Earth's magnetic field and its secular variation. Superim posed on a postulated main meridional flow consisting of fluid upwelli ng at the equator and downwelling at the poles is a secondary how syst em in which fluid spreads out from a point beneath the triple junction of the South American, African and Antarctic lithospheric plates, tra vels in a thin layer at the surface of the core and then descends in t he vicinity of Indonesia. Except in the region of the south Atlantic O cean, the inferred secondary flow of fluid in the outermost core tends to mimic the directions in which the major lithospheric plates move w ith respect to ''hot spots'' thereby supporting the idea that most of the major features of the non-dipole portion of the geomagnetic field are caused and controlled by mantle convection and remain ''stationary '' on an historic time scale.