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D. T. Hall (1), G. R. Gladstone (2), H. W. Moos (1), F. Bagenal (3), J. T. Clarke (4), P. D. Feldman, M. A. McGrath, N. M. Schneider, D. E. Shemansky, D. F. Strobel, J. H. Waite
1) Center for Astrophysical Sciences, Johns Hopkins University,
Charles and 34th Sts., Baltimore MD 21218
2) Southwest Research Institute, 6220 Culebra Rd. San Antonio,
TX 78284
3) University of Colorado, Boulder CO 80309
4) University of Michigan, 2455 Hayward, Ann Arbor, MI 48109-2143
(For other author affiliations, contact first author at: dthall@pha.jhu.edu)
We present the first Extreme Ultraviolet Explorer satellite observation of the Jupiter system, obtained during the two day period 1993 March 30 through April 1, which shows a rich emission line spectrum from the Io plasma torus spanning wavelengths 370 to 735 Å. The emission features correspond primarily to known multiplets of oxygen and sulfur ions, but a blended feature near 372 Å is a plausible NaII transition. The summed detected energy flux of (7.2 +/- 0.2)E-11 erg cm-2 sec-1 corresponds to a radiated power of approximately 4E+11 Watts in this spectral range. All ANSA emissions show a distinct dawn-dusk brightness asymmetry and the measured dusk/dawn ratio of the bright SIII 680 Å feature is 2.3 +/- 0.3, significantly larger than the ratio measured by the Voyager spacecraft UV instruments. A preliminary estimate of ion partitioning indicates that the oxygen/sulfur ion ratio is approximately 2, compared to the value approximately 1.3 measured by Voyager, and that [NaII]/[e] > 0.01.
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