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R. Prang\'e (IAS, Orsay, France), D. Rego (UCL, London, UK), J. E. P. Connerney (NASA/GSFC), P. Zarka, J. Queinnec (DESPA, Obs. Meudon, France)
A set of HST FOC images taken in the H2 bands near 1550 Å is used to infer the morphological properties of the steady state Jovian FUV aurorae with emphasis on issues best addressed using the excellent spatial resolution (high latitude or small auroral features). We establish the improvement of the new VIP4 magnetic field model over previous ones at all latitudes. The north-south conjugacy of the main oval is now correctly accounted for, despite small systematic discrepancies. This oval is amazingly narrow (down to 80 ± 50 km), bright, and quite variable (100 kR to 1-2 MR, i.e., peak input flux of ~10-200 ergs cm-2 s-1). We discuss its structure, in latitude and longitude, consistent with precipitation by pitch angle scattering. Fainter narrow ovals appear on the north polar cap, presumably at the footprint of open field lines. Both polar caps are partly covered by a faint diffuse emission, confined to the afternoon sector in MLT. A bright feature extending across the north polar cap along the 160 deg. meridian (System III), might be not a specific auroral feature but rather a region where polar cap emissions are intensified, maybe by a solar wind driven ionospheric process. Equatorward of the main oval, we identify a belt of moderate and stable emission, attributed to a precipitation process acting from the Io torus to the distant magnetosphere. Longitudinally confined bright areas lie in the same latitude range and consist of series of short segments of concentric arcs. We also present the discovery of a narrow faint oval at the footprint of Io's orbit. Finally, we confirm that the FUV footprints of the Io flux tube are very small (a few 100 kms or less), implying an interaction close to Io. The input energy flux in this spots is huge and variable (0.8-5 x 1011 W).
The author(s) of this abstract have provided an email address for comments about the abstract: prange@ias.fr