Experimental Studies of Convection in the Earth's Core

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AurnouEAR-0229791This proposal requests funding for work in a new experimental fluidmechanics laboratory at UCLA. The lab will utilize two, new powerfuldiagnostic techniques to provide high-resolution, quantitative velocitymeasurements of simulated convection in the Earth's outer core. Theresults will test long-held theories regarding the properties ofconvective flows in core fluids and will provide a detailedcharacterization of flow dynamics at nearly planetary parameter values.The first project will use the recently developed technique of acousticDoppler velocimetry to study convecting liquid metals, which havephysical properties similar to that of the molten outer core. Theresults will test the linear stability theory of rotatingmagnetoconvection, the foundation of modern dynamo theory. Establishedby Chandrasekhar in the 1950's, this stability theory has only undergonea single prior experimental investigation that reached the asymptoticregime. The second project will utilize the optical technique ofparticle image velocimetry (PIV), applying it to a rotating sphericalshell of convecting water, a set-up that mimics the dynamics and thegeometry of the outer core. PIV will provide, for the first time,quantitative measurements of the flow fields (velocity, vorticity andhelicity) 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 measureconvection in the polar regions, which have not been studied extensivelybut now appear to be significant. Together, these state-of-the-artacoustic and optical velocimetry techniques will provide benchmarks fornumerical and theoretical studies of core convection and the geodynamo.They will also generate the highest resolution experimental convectiondata to date for interpreting geomagnetic and seismic observations ofthe deep Earth.