ROTATIONAL ANISOTROPY OF THE JOVIAN MAGNETOSPHERE AT HIGH-LATITUDES

The Ulysses spacecraft passed through the Jovian system in February 19 92. Its trajectory, determined by its interplanetary mission, directed the spacecraft to the previously unexplored high-latitude regions of the Jovian magnetosphere. Like Pioneers 10 and 11 and the two Voyagers , Ulysses entered the magnetosphere in the near equatorial morning sec tor, but unlike the previous spacecraft, Ulysses exited at high latitu de near local dusk. This report considerably extends the work of Lanze rotti et al. (1993) by analyzing the extent of rotational anisotropy a t high southern Jovigraphic latitudes attained by Ulysses during its o utbound pass. Using data acquired by the Ulysses Heliosphere Instrumen t for Spectral, Composition, and Anisotropy at Low Energies (HI-SCALE) , we report some evidence of corotational flow in the high-latitude du skside magnetosphere. On the inbound pass the Ulysses HI-SCALE instrum ent observed anisotropies indicating partial corotation and a corotati on lag. These data are consistent with Voyager plasma and energetic pa rticle results. This is the first report of flow in the corotational d irection from 44-57 R(J) in the duskside, high-latitude Jovian magneto sphere. There is strong evidence for a substantially reduced corotatio nal anisotropy in this duskside region relative to a comparable radial distance range, 47-59 R(J), on the dayside.