Global Context of the Galileo-E6 Observations of Jupiter's White Ovals

Galileo Solid State Imaging (SSI) data taken during the E6 orbit on February 19, 1997 offer a brief, high-resolution glimpse of Jupiter's White Ovals. These data can be used to infer relative cloud heights and systematic rotations over a small area of latitude and longitude (approximately 20° by 30°) around the White Ovals. To fully understand the behavior of these cloud systems, however, a longer time span of global data is necessary. In this paper, we utilize ground-based Voyager and Hubble Space Telescope data to interpret the Galileo images. We find that the White Ovals' translation rates have slowed from 0.39 deg day−1during the Voyager era to 0.13 deg day−1in 1996 and they, along with three smaller anticyclonic systems, have coalesced into a system of alternating cyclonic and anticyclonic systems that has not been observed before. The largest of the ovals, BC, is now impeding the eastward motion of the system, causing more rapidly translating anticyclonic cells to catch the system and increase the westward extension of the equally spaced features. Rotational velocities for BC and a small anticyclonic system at 42°S have also been measured and peak at 120 m sec−1for both systems, comparable to the Mitchellet al. (J. Geophys. Res.86,8751–8757) measurements of BC and the Great Red Spot (GRS) from Voyager data. The motion of individual features and of the whole system in the ambient wind flow is discussed.