Persistence and Variability of Large-Scale Longitudinal Structure in the Io Plasma Torus

R. C. Woodward Jr., F. L. Roesler (U. Wisc.), R. J. Oliversen (NASA/GSFC), F. Scherb (U. Wisc.), H. W. Moos (JHU)
Abstract: The first spectroscopic FUV images of Io revealed a two-fold brightening of all bright neutral emission lines over the four-hour HST "visit" on October 14, 1997 [Roesler 1999]. We subsequently found simultaneous brightenings in [O I] 6300Å Io emission [Oliversen 2001] and [S II] 1256Å torus emission [Woodward 2001a]. A preliminary analysis of our extensive set of [S II] 6731Å groundbased images of the Io torus [Woodward 1999] showed a longitudinal emission enhancement from ~ 70°-160° [Woodward 2001b]. We now find that this enhancement was present in September 1997 as well, but at significantly reduced contrast (see figure). In this work, we study the persistence and variability of this and other longitudinal structures in the torus, based on STIS and groundbased data. This work was supported in part by NASA grants NAS5-30131, NAG5-6787, NAG5-6546, and RTOP 344-32-30.

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Markup on above figure omitted for clarity. Click on figure for full published version; also see figure 2.
Copyright © 2001 R. Carey Woodward Jr. and/or the Board of Regents of the University of Wisconsin, as their interests lie. This work was presented as a "poster paper" at the 33rd meeting of the Division for Planetary Sciences of the American Astronomical Society (November 27-December 1, 2001). The abstract was published in Bull. American Astron. Soc. (33, 1065), which is copyright © 2001 by the American Astronomical Society. You may view and download this work for your personal use, but may not redistribute it or make commercial use of it without permission.