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M. B. Vincent, J. T. Clarke, G. E. Ballester (U. Michigan), W. M. Harris (U. Wisconsin), R. A. West (JPL)
Jupiter's polar stratospheric aerosols are probed by ultraviolet (UV) images taken with the Hubble Space Telescope's Wide Field and Planetary Camera 2. These aerosols may be generated by auroral-driven chemistry and/or concentrated by the winds. Although about 400 km of vertical separation exists between Jupiter's far-UV auroral emissions and the altitude probed by the UV images, auroral aligned features were detected in images taken from 1994 to 1997.
We discovered an auroral aligned UV darkened segment that generally extended over 100-260o System III longitude, and 39-53oN planetocentric latitude, or near the equatorward-most portion of the north auroral oval. The segment was ~20 42oN in the F160W images, and was also present in the F218W and F255W images. Auroral-driven winds and/or eddy mixing may provide the means to meridionally transport these aerosols from the polar hood to the darkened segment. Retrograde winds in the stratosphere (Vincent, Ph.D. Dissertation) could transport the aerosols westward over the length of the segment before sedimentation removes them. We observed no single type of feature in the F218W and F255W images that was consistently aligned within the outline of the north auroral oval, however, several transient features were observed. It is not certain whether these transient features were associated with auroral processes, or just coincidentally aligned. A "South Dark Patch" (SDP) was consistently observed within the south auroral oval. The SDP appears as an area ~33 polar hood in the F218W images. The SDP appeared small in July 1994 and increased in size afterwards. This suggests a possible seasonal effect, since for the southern hemisphere the beginning of summer and fall occurred in July 1994 and late 1997, respectively. This work is supported by WFPC2 grant JPL 959122 from JPL to the University of Michigan.