DPS 2001 meeting, November 2001
Session 17. Io, Tori, and Satellite Atmospheres Posters
Displayed, 9:00am Tuesday - 3:00pm Saturday, Highlighted, Wednesday, November 28, 2001, 10:30am-12:30pm, French Market Exhibit Hall

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[17.08] Substantial Io Torus Variability 1998-2000

N.M. Schneider, R. Morris, A Park (LASP, U. Colorado), M Kueppers (Uni. Bern, Switzerland)

Analysis of torus observations from the KPNO 4m telescope during the Cassini encounter suggest that the structure of the torus was different from recent years based on comparable long-slit spectra. Specifically, the brightest S+ 6731Å\ emission came from the cold torus, not the ribbon or warm torus. This is not to say that the ribbon had disappeared: it is still evident in our data but it does not dominate the spatial profile as it has in observations in 1998 and 1999. In 1998-1999, the cold torus appeared as a bump on the inside edge of the ribbon. In 2000, the cold torus is well resolved from the ribbon, and brighter than the ribbon at virtually all longitudes. Further analysis will determine if the spatial change is accompanied by luminosity changes, and whether the torus density or ionization state has changed. Comparison with Cassini and other groundbased observations may place the variability in context, though sufficent data are probably not available to determine the cause or effect of the torus variability.

This work has been supported by NASA's Planetary Astronomy Program

The author(s) of this abstract have provided an email address for comments about the abstract: nick.schneider@lasp.colorado.edu

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