THE MORPHOLOGY OF THE NORTH JOVIAN ULTRAVIOLET AURORA OBSERVED WITH THE HUBBLE-SPACE-TELESCOPE

A series of six images covering a complete rotation of the north polar region of Jupiter were Obtained in February 1993 with the Faint Object Camera on board the Hubble Space Telescope. These images provide the first global picture of the morphology of the Jovian ultraviolet aurora observed from Earth orbit. The camera passband was centered near 153 nm, a region dominated by the H-2 Lyman bands and continuum. The successive exposures, taken approximately 90 min apart, are used to construct a polar view of the auroral zone. It is found that the auroral emissions do not exactly follow the footprint of a constant L-shell although the size of the oval and its location agree best with the footprints of the similar or equal to 30 R(J) field line in the GSFC O-6 model of the Jovian magnetic field. The displacement between the observed auroral zone and the theoretical oval may indicate a possible distortion of the Jovian magnetic field lines near the surface. A comparison with two images at the same wavelength obtained 8 months earlier shows that the : main morphological features are persistent, in spite of changes in the detailed emission distribution. Small scale features with characteristic sizes of similar to 1000 km are observed along the auroral oval. The change of morphology observed as a function of the System III longitude appears as a persistent characteristic of the morphology of the north polar aurora.