HR: 0800h
AN: P51B-1426    [Abstracts]
TI: Tangent Cylinder Effects in Jovian Convection
AU: * Andreadis, S J
EM: sandread@jhu.edu
AF: Johns Hopkins University, Dept. of Earth and Planetary Sciences, 3400 N. Charles St, Baltimore, MD 21218 United States
AU: Olson, P
EM: olson@jhu.edu
AF: Johns Hopkins University, Dept. of Earth and Planetary Sciences, 3400 N. Charles St, Baltimore, MD 21218 United States
AB: Two properties of Jupiter's dynamics that are still not well understood are the extent and driving force of the zonal winds and the meridionally-independent heat loss. These may be linked by the presence of a tangent cylinder effect in the interior of the planet. A tangent cylinder could be formed by rotational constraints at the molecular to metallic hydrogen transition at ~0.8 jovian radii. Evidence for the existence of a tangent cylinder can be seen in pictures of Jupiter's northern hemisphere taken by the Cassini spacecraft en route to Saturn. At the latitude corresponding to the surface projection of the tangent cylinder, cloud motions are separated into a equatorial region with large scale zonal motions and a polar region with smaller scale, chaotic motions. To investigate tangent cylinder effects in Jupiter, we study a 3-D rotating thermal convection numerical simulation in a thin shell ($r_{inner}/r_{outer}=0.75$). Thermal convection solutions are obtained over a range of Rayleigh numbers $Ra$, for both rigid and free lower stress boundary conditions. The zonal winds and heat loss at the top of the shell and meridional flow throughout the shell are compared with observations. The numerical zonal winds recover some characteristics of observed winds on Jupiter, such as the large prograde equatorial zonal jet. Furthermore, at $Ra>4E6$, alternating jets appear poleward of the tangent cylinder, with wavelength similar to those seen in the Cassini image. Equatorial winds outside of the tangent cylinder are driven by the Reynold stresses from sloping fluid columns. Winds inside the tangent cylinder are non-geostrophic and require a different mechanism for their generation. Also at $Ra>4E6$, heat loss at the top of the shell is greater inside the tangent cylinder than outside. The tangent cylinder acts as a barrier to fluid motions, preventing meridional heat transfer and enhancing interior heat loss at the poles. This offers an explanation for why the total (interior + solar) heat loss from Jupiter is observed to be nearly independent of latitude.
DE: 8147 Planetary interiors (5430, 5724)
DE: 5707 Atmospheres--structure and dynamics
DE: 5724 Interiors (8147)
DE: 6220 Jupiter
SC: Planetary Sciences [P]
MN: 2004 AGU Fall Meeting