Interaction of Eddies and Mean Zonal Flow on Jupiter as Inferred From Voyager 1 and 2 Images

Voyager 1 and 2 narrow-angle frames were used to obtain displacements of features at resolutions of 130 km over time intervals of 1 Jovian rotation. The zonal velocity d was constant to 1.5% during the 4 months between the Voyager 1 and 2 encounters. The latitudes of the zonal jet maxima (extrema of •) are the same as inferred from earth-based observations extending over the past 80 years. The curvature of the velocity profile d•-d/dy 2varies with latitudinal coordinate y in the range from -3/• to +2/•, where/• is the planetary vorticity gradient. The barotropic stability criterion is violated at about 10 latitudes between +60 ø. The eddy momentum flux variation with latitude u'v' is positively correlated with dt•/dy for both Voyager 1 and 2 data. The rate of conversion {K'[(} of eddy kinetic energy into zonal mean kinetic energy is in the range 1.5-3.0 Wm -•-, for a layer 2.5 bar deep. The time constant for resupply of zonal mean kinetic energy by eddies is in the range 2-4 months, less than the interval between Voyager encounters. The rate of energy conversion is more than 10% of the total infrared heat flux for Jupiter, in contrast with earth where it is only 0.1% of the infrared heat flux. This hundred-fold difference suggests that the thermomechanical energy cycles are very different on the two planets.