Physics
Scientific paper
Dec 2009
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2009agufm.p31b1244b&link_type=abstract
American Geophysical Union, Fall Meeting 2009, abstract #P31B-1244
Physics
[1213] Geodesy And Gravity / Earth'S Interior: Dynamics, [1507] Geomagnetism And Paleomagnetism / Core Processes, [5430] Planetary Sciences: Solid Surface Planets / Interiors
Scientific paper
Tidal forcing at diurnal periods drives a flow in the liquid cores of planets, altering the nutation of these bodies. An approximate description of the flow in an inviscid fluid is comprised of a uniform vorticity and a potential flow to satisfy boundary conditions. This flow (often called Poincare flow) is unable to satisfy boundary conditions when the solid inner core tilts relative to the mantle or when the ellipticity of the inner-core boundary differs from the ellipticity of the core-mantle boundary. A numerical solution is used to show that internal shear layers develop when Poincare flow fails. The thickness of the shear layers scale as E1/3, where E is the Ekman number. The total viscous dissipation also scales as E1/3 when stress-free boundary conditions are assumed. Extrapolating E to realistic values for planetary cores suggests that viscous dissipation is negligible. However, shear layers also induce electric currents when the core is permeated with a magnetic field. Scaling arguments for a weak magnetic field suggest that the resulting ohmic dissipation is proportional to E-2/3. This estimate is supported by numerical calculations with E = 10-4 to 10-6. The singularity at vanishingly small values of E is avoided by the influence of the Lorentz force on the flow. The resulting ohmic dissipation should be detectable in observations of the Earth’s nutation, but it is insufficient to explain all of the dissipation that is actually observed. Strong magnetic coupling at the core-mantle and inner-core boundaries probably accounts for most of the observed dissipation.
No associations
LandOfFree
Tidal flow and dissipation in planetary cores does not yet have a rating. At this time, there are no reviews or comments for this scientific paper.
If you have personal experience with Tidal flow and dissipation in planetary cores, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Tidal flow and dissipation in planetary cores will most certainly appreciate the feedback.
Profile ID: LFWR-SCP-O-1770524