36th DPS Meeting, 8-12 November 2004
Session 18 Outer Planets
Poster I, Tuesday, November 9, 2004, 4:00-7:00pm, Exhibition Hall 1A

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[18.07] The Relationship between Eddies and Zonal Flow on Jupiter: Results from the Cassini Flyby

C. Salyk, S. Ewald, A.P. Ingersoll (California Institute of Technology), J. Lorre, A. Vasavada (Jet Propulsion Laboratory)

Using images of Jupiter from the Voyager missions, Ingersoll et al. (JGR 86, p. 8733-8743, 1981) found that longitudinally averaged eddy momentum flux, \overline{u'v'}, was positively correlated with the variation of zonal velocity with latitude, d\bar{u}/dy, implying that Jupiter's eddies are supplying energy to the zonal wind flow. Using a conservative estimate of the mass being transported in this process, they derive a power per unit area of between 1.5 and 3 W m-2. The amount of energy transferred would thus be more than 10% of Jupiter's thermal radiation; in comparison, Earth's eddies transfer an amount of energy that is about 0.1% of its emitted thermal energy. The analysis of Ingersoll et al., however, was challenged by Sromovsky et al. (JAtS 39, p. 1433-1445, 1982) who demonstrated that sampling biases could skew the results of such a study. Among their concerns were the possibility that a few, well-sampled areas of the planet were contributing disproportionately to the observed correlation, that the longitudinally averaged \overline{u'v'} was strongly affected by values of u'v' far from the median of the sample, and that the human eye, which was used for feature correlation, may have introduced unknown biases. After more than 20 years, we revisit these issues. We report results of an analysis of eddy momentum flux using images from the recent Cassini flyby of Jupiter analyzed with an automatic feature-tracker, which provided the advantages of more even planetary coverage, a greater number of tracked features and the absence of human bias. We find a similar correlation between \overline{u'v'} and d\overline{u}/dy. We will present this result and our estimate of the eddy energy transfer rate, as well as several tests demonstrating the robustness of our conclusions.

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Bulletin of the American Astronomical Society, 36 #4
© 2004. The American Astronomical Soceity.