This is a Small Grant for Exploratory Research proposal to conduct laboratory fluid dynamical experiments on flow in the Earth's liquid outer core. The PIs will investigate the combined effects of Earth's spin and precession on buoyantly-driven flow in a fluid spheroid, whose shape approximates the shape of the core- mantle boundary. The purpose is to determine the influence of unsteady rotation on core motions, arising from the 23,000 yr luni- solar precession of the mantle. In particular, the relative importance of buoyancy and precessional effects in controlling the structure of fluid motions just below the core-mantle boundary, where geomagnetic secular variations have been used to infer the pattern fluid motion will be determined. The PIs will carry out a series of experiments using a liquid-filled spheroidal cavity mounted on a rotation/precession apparatus, with boundary temperature control. This is the first time the effects of convection and precession have been investigated simultaneously in a rotating fluid with the geometry of the Earth's core. They intend to (1) determine the pattern of flow due to thermal buoyancy and due to precession, and (2) measure the zonal flows, meridional flows and differential rotation produced by precession and convection. The ultimate goal is to develop a comprehensive experimental approach to the processes that underlay magnetic field generation in the Earth's core.
