HR: 17:45h
AN: GP44A-08    [Abstracts]
TI: Thermal Winds in the Tangent Cylinder
AU: * Aurnou, J
EM: aurnou@ucla.edu
AF: UCLA Earth & Space Sciences, 595 Charles Young Dr. East, Los Angeles, CA 90095-1567 United States
AU: Aubert, J
EM: aubert@ipgp.jussieu.fr
AF: Institut de Physique de Globe de Paris, 75251 Paris, Paris, Cedex 05 France
AU: Amit, H
EM: hagay@jhu.edu
AF: Johns Hopkins University, Earth and Planetary Sciences, 34th and N. Charles St., Baltimore, MD 21218 United States
AU: Andreadis, S
EM: sandread@jhu.edu
AF: Johns Hopkins University, Earth and Planetary Sciences, 34th and N. Charles St., Baltimore, MD 21218 United States
AU: Olson, P
EM: olson@jhu.edu
AF: Johns Hopkins University, Earth and Planetary Sciences, 34th and N. Charles St., Baltimore, MD 21218 United States
AB: Thermal winds inside the tangent cylinder naturally develop in models of core fluid dynamics and can explain a broad array of deep Earth observations. The tangent cylinder, the imaginary axial cylinder that circumscribes the inner core equator, acts to separate the outer core into three distinct regions: outside the tangent cylinder and inside the tangent cylinder in the northern and southern hemispheres. Here we present the results of laboratory convection experiments and numerical dynamo models that demonstrate that thermal winds dominate the large-scale flow inside the tangent cylinder. These thermal winds are azimuthal zonal flows that are retrograde (westward) just below the core-mantle boundary and prograde (eastward) just above the inner core boundary. In both laboratory and numerical studies, the typical zonal velocity within the tangent cylinder, U, follows an asymptotic thermal wind scaling law: U ~ (B/Ω)^1/2, where B is the buoyancy flux in the Earth's core and Ω is the planetary angular velocity. Further support for tangent cylinder thermal winds comes from frozen flux models of flow below the core-mantle boundary. In these models, strong retrograde zonal flows exist at high latitudes and then drop off sharply at lower latitudes outside the tangent cylinder. In addition, we present models of inner core super-rotation based on electromagnetic coupling of prograde thermal wind flows at the inner core boundary. Together these forward and inverse models suggest that thermal winds inside the tangent cylinder are an integral component of the large-scale dynamics of the Earth's core.
DE: 1213 Earth's interior: dynamics (1507, 7207, 7208, 8115, 8120)
DE: 1507 Core processes (1213, 8115)
DE: 1510 Dynamo: theories and simulations
DE: 1560 Time variations: secular and longer
DE: 5440 Magnetic fields and magnetism
SC: Geomagnetism and Paleomagnetism [GP]
MN: Fall Meeting 2005