COMPARISON OF THE STRUCTURE AND DYNAMICS OF JUPITER GREAT RED-SPOT BETWEEN THE VOYAGER-1 AND VOYAGER-2 ENCOUNTERS

We have consistently navigated the highest resolution images available of Jupiter's Great Red Spot (GRS) from the Voyager ISS experiment. Fr om them we have measured apparent displacements of cloud features arou nd and within the Red Spot which can be interpreted as wind vectors. W e have used the wind field information to determine the circulation ch aracteristics of the collar and to map the relative vorticity and hori zontal divergence of the central GRS region, Color ratios and ground-b ased data have been used to complement these observations. Derived qua ntities from the IRIS data set taken simultaneously with the Voyager i mages have been obtained in order to determine the thermal structure, infrared cloud opacity, NH3 abundance, and para H-2 fraction above the Great Red Spot, There is evidence of non-chaotic activity in the cent ral region of the Red Spot. Small eddy structures consisting of cohere nt cloud features with apparently two-dimensional turbulent motions ar e present in this region along with larger classical cyclonic vortices , The surrounding anticyclonic collar circulates with higher velocitie s and appears to be detached from the core by an abrupt transition reg ion, The central region appears to be elevated over the surrounding co llar and exhibits evidence for upwelling and some outflow of material. Differences in the collar structure and velocity profiles between the Voyager encounters can be attributed to differences in the ingestion rate of westward-moving South Equatorial Belt vortices caused by a blo cking South Tropical Zone Disturbance which, moving eastward, overtook and passed the Red Spot between the two encounters. This disturbance appears to temporarily increase in brightness during conjunctions with the Red Spot and has been tracked for 20 years. (C) 1996 Academic Pre ss, Inc.