THE STRUCTURE OF THE IO TORUS

New high-quality images of the Io plasma torus allow improved measurem ents of its structure. We have analyzed almost 80 images of [S II] 673 1 Angstrom emissions from S+ revealing interesting structures in the r adial, local time, latitudinal, and longitudinal dimensions. The avera ged radial profile shows a maximum intensity at 5,71R(J), significantl y inside Io's orbit at 5.91R(J). The radial structure is offset 0.14R( J) toward the dawn (east) side of Jupiter, and emissions are similar t o 20% brighter on the dusk (west.) In the latitudinal dimension, the p lasma torus ''illuminates'' the centrifugal equator of Jupiter's magne tic field. The centrifugal equator derived from our data is generally consistent with the ''O6 + current sheet'' field model derived by spac ecraft measurements, but some unexplained differences stand out. We fi nd lower ion temperatures in the ''active sector,'' perhaps a direct c onsequence of higher emission rates there. We also report the puzzling result that the ribbon (the most prominent plasma feature encircling Jupiter) is not centered on Jupiter's rotation axis or on the offset m agnetic axis. The origin of the structure we describe here remains eni gmatic.