This work was originally presented as a "poster paper" at the
Spring
2000 meeting
of the American
Geophysical Union.
Here you may view a hypertext version of the paper, both with and
without frames, or download a
compressed PostScript version
or an uncompressed PDF version
(you may have to shift-click those links). In each figure, you can view a
larger version of a graphic by clicking it (or download the larger version
by shift-clicking it if your browser works that way).
Address queries on this work to
woodward@physics.wisc.edu.
Copyright statement follows.
Because Io was near western (receding) elongation when these data were
acquired, the torus emission observed by STIS was strongly influenced by
line-of-sight geometry, and therefore by the precise location of the
torus. The torus radial position and scale height are known to vary with
magnetic longitude, local time, and other factors in ways that are not well
understood; therefore, the groundbased torus images, in addition their
intrinsic interest, are crucial in interpreting the spatially limited STIS
data: with the aid of a semiempirical model of the plasma torus [Woodward and
Smyth 1994], these images allow us to model the underlying torus emission in
the STIS data, and thus to separate it from emission local to Io, and
distinguish true temporal variations from the effects of viewing geometry. In
particular, we will examine the behavior of the torus and near-Io ion
emissions during a brightening of neutral iogenic emissions at 06:00 UT.
Copyright © 2000
R. Carey Woodward Jr. and/or
the Board of Regents of the
University of Wisconsin,
as their interests lie. You may view and
download this work for your personal use, but may not redistribute it or make commercial use of it without permission. The
abstract published in
Eos
81(19), S290, 2000.
During conversion from poster to
hypertext format, an error in the data shown in fig. 7C was
discovered; that figure, the section entitled Brightening, and the final
summary item have been changed accordingly from the originally presented
version. Other minor syntactic and stylistic changes have also been made.
Abstract
On 14 October 1997 Io and the Io plasma torus were simultaneously observed by
three different instruments: the HST Space Telescope Imaging Spectrograph
(STIS) obtained six spectrally resolved images in the 1200–1700Å
range of a
2" × 25" rectangle encompassing Io [Roesler et
al. 1999]; a nondispersing imager at the McMath-Pierce west auxiliary
telescope [Woodward et al. 1999] obtained nine images of the east ansa of the
plasma torus in [S II] 6731Å; and the echelle spectrograph on the
McMath-Pierce main telescope obtained eighteen spectra of [O I]
6300Å from a 5" × 5"
aperture centered on Io [Scherb et
al. 1998]. Io's neutral emissions in these datasets have been discussed
elsewhere. Here we will examine the emissions of S II, both near Io
and in the torus, primarily in the STIS dataset.
References
1University of Wisconsin—Madison (Dept. of Physics)
2NASA Goddard Space Flight Center
3Atmospheric & Environmental Research, Inc.
4Johns Hopkins University (Dept. of Physics & Astronomy)
5Visiting Astronomer, National Solar Observatory, National
Optical Astronomy Observatories, which is operated by the Association of
Universities for Research in Astronomy, Inc., under contract with the
National Science Foundation