Experimental Studies of Convection in the Earth's Core

University Of California-Los Angeles, Los Angeles CA

Investigators

Abstract

Aurnou EAR-0229791 This proposal requests funding for work in a new experimental fluid mechanics laboratory at UCLA. The lab will utilize two, new powerful diagnostic techniques to provide high-resolution, quantitative velocity measurements of simulated convection in the Earth's outer core. The results will test long-held theories regarding the properties of convective flows in core fluids and will provide a detailed characterization of flow dynamics at nearly planetary parameter values. The first project will use the recently developed technique of acoustic Doppler velocimetry to study convecting liquid metals, which have physical properties similar to that of the molten outer core. The results will test the linear stability theory of rotating magnetoconvection, the foundation of modern dynamo theory. Established by Chandrasekhar in the 1950's, this stability theory has only undergone a single prior experimental investigation that reached the asymptotic regime. The second project will utilize the optical technique of particle image velocimetry (PIV), applying it to a rotating spherical shell of convecting water, a set-up that mimics the dynamics and the geometry of the outer core. PIV will provide, for the first time, quantitative measurements of the flow fields (velocity, vorticity and helicity) that are believed to be essential components of the geodynamo, but have never been measured adequately by experimental means. Furthermore, the experimental design will enable PIV to measure convection in the polar regions, which have not been studied extensively but now appear to be significant. Together, these state-of-the-art acoustic and optical velocimetry techniques will provide benchmarks for numerical and theoretical studies of core convection and the geodynamo. They will also generate the highest resolution experimental convection data to date for interpreting geomagnetic and seismic observations of the deep Earth.