DPS Pasadena Meeting 2000, 23-27 October 2000
Session 35. Galilean Satellites - Atmospheres and Tori Posters
Displayed, 1:00pm, Monday - 1:00pm, Friday, Highlighted Tuesday and Thursday, 3:30-6:30pm, C101-C105, C211

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[35.15] UVSTAR Observations of the Io Plasma Torus

G.E. Ballester, F. Herbert, A.L. Broadfoot, B.R. Sandel (LPL, U. Arizona)

We present results from UV observations of the Io plasma torus performed by UVSTAR (Ultraviolet Spectrograph Telescope for Astronomical Research) on the STS-95 shuttle flight. UVSTAR consists of two 12 inch telescopes, each with a long-slit spectrograph at the prime focus and a detector consisting of a microchannel plate feeding into a CCD. The spectrographs cover the EUV 500--950{\thinspace Å} and FUV 800--1300{\thinspace Å} spectral regions. Over the period of 1-6 November 1998, five ~15-minute observations were made simultaneously in both channels, and 5 additional observations were made in the FUV. Spectrally-resolved images of the torus were obtained showing several emission features from singly- and doubly-ionized sulfur and oxygen collisionally excited by the torus electrons. Cross-calibration is achieved by comparison of the SII{\,\lambda908} multiplet which is present in both the EUV and FUV spectra.

Emissions from the east and west ansae are separated within a given exposure, yielding data at a total of 10 longitudinal regions. A one-dimensional emission spectrum is deconvolved from each dataset, using the SIII{\,\lambda685} feature as an approximation of a monochromatic torus image. Information on the torus electron temperature, total plasma density, and relative ion abundances will be derived for each ansa by model fitting, as a function of System III longitude, Io phase and time.

Support for this work has been provided by NASA grants NAG5-4158, NAG5-6362 and NAG5-8051 to the University of Arizona.

The author(s) of this abstract have provided an email address for comments about the abstract: gilda@vega.lpl.arizona.edu

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