Physics
Scientific paper
Dec 2006
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2006agufm.p41c1287h&link_type=abstract
American Geophysical Union, Fall Meeting 2006, abstract #P41C-1287
Physics
1507 Core Processes (1213, 8115), 3314 Convective Processes, 3367 Theoretical Modeling, 5704 Atmospheres (0343, 1060), 5724 Interiors (8147)
Scientific paper
Observations of Saturn's surface have revealed a fascinating time-variable dynamical history. In 1990 a powerful storm called a Great White Spot erupted near the equator and filled the equatorial region with easily visible flow structures. In the interval between the Voyager missions of 1980 and 1981 and the current Cassini mission, the wind velocity of Saturn's equatorial jet seems to have changed. In the same time interval, estimates of the planet's rotation period, based on Saturn's kilometric radio (SKR) emissions, have increased by six to eight minutes (an apparent rotation rate slowdown of roughly 1%). While a link between the 1990 great white spot, the equatorial jet variability and the apparent planetary rotation slowdown has been suggested, no causal relationship between these phenomena has been proposed. We will present simulations of Boussinesq rotating convection in a 3D spherical shell that allows for angular momentum transfer between the outer shell fluid and the rigid inner sphere. The simulation dynamics are dominated by quasiperiodic convective bursts. Each burst event gives rise to a significant change in the latitudinal profile of the equatorial jet velocity, followed by retrograde torque on the inner spherical boundary and subsequent slowdown of the rigid inner sphere. The results lead us to propose that the Great White Spot was the surface expression of a deep convective burst that caused changes in the equatorial winds and a decrease in the rotation rate of Saturn's deep-seated magnetic field source region.
Aurnou Jonathan
Heimpel Moritz
Wicht Johannes
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