HR: 0800h
AN: DI31A-0254    [Abstracts]
TI: Preliminary Results From a Three-dimensional Numerical Simulation of Compositional Convection in the Earth's Fluid Core
AU: * Chen, Q
EM: qnchen@math.ucla.edu
AU: Roberts, P H
EM: roberts@math.ucla.edu
AB: Compositional buoyancy is believed to be important in driving core convection responsible for the geodynamo. As the Earth cools, heavy elements are segregated out of core fluid alloy and become part of the solid inner core (SIC), light elements and latent heat being simultaneously released from the inner core boundary (ICB). This release is probably non-uniform over the ICB, and occurs in discrete buoyant plumes or "jets". It has been argued by Loper and Moffatt that this discreteness has major implications for small- scale core dynamics. The aim of this project is to investigate this suggestion through numerical simulations. In the fluid outer core (FOC), the fluid presumably has very small compositional diffusivity κ_ξ ~ O(10^{- 9})m²/s and viscosity ν ~ O(10^-6)m²/s. If the light elements are ejected out of the ICB as a jet with velocity scale 0.001 m/s < U_jet < 0.1m/s and length scale (the width of the jet) 1 m < L < 10³ m, the jet's Reynolds number would be between 10³ and 10¹⁰ and its compositional Prandtl number would be O(10³). For such large Reynolds and Prandtl numbers, severe numerical instability is unavoidable if the numerical resolution is not high enough. We report on a novel numerical approach to overcome this difficulty. Our mathematical model is three-dimensional compositional convection in a bounded fluid layer (representing the FOC) driven by a buoyant jet from the bottom boundary (representing the ICB). Some preliminary results from these calculations will be presented.
DE: 0500 COMPUTATIONAL GEOPHYSICS (3200, 3252, 7833)
DE: 5400 PLANETARY SCIENCES: SOLID SURFACE PLANETS
SC: Study of the Earth's Deep Interior [DI]
MN: 2007 Fall Meeting