DPS 2001 meeting, November 2001
Session 9. Cassini and Galileo at Jupiter Posters
Displayed, 9:00am Tuesday - 3:00pm Saturday, Highlighted, Tuesday, November 27, 2001, 5:00-7:00pm, French Market Exhibit Hall

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[9.01] Radial Structure of the Io Plasma Torus from Cassini UVIS

A. Steffl, I. Stewart, F. Bagenal, N.M. Schneider (CU-Boulder, LASP)

On December 30, 2000, the Cassini spacecraft made its closest approach to Jupiter. The UVIS instrument (wavelength range of 560-1180 ) obtained a series of high spatial-resolution spectra of the Io plasma torus in the EUV. These spectra were taken with the low-resolution slit (2 mrad x 64 mrad) perpendicular to Jupiter's equator, and were obtained by scanning across a radial distance of 3-10 RJ. During the observations, the spacecraft was approximately 200 RJ away from the planet, resulting in a spatial resolution of ~ 0.4 RJ. We present a high signal-to-noise spectrum of the torus containing all spectral lines with equatorial brightness greater than 5 Rayleighs. Additionally, we present the brightness of several prominent spectral lines versus radial distance, specifically, the O II 834 to S III 680 brightness ratio as an indicator of the oxygen to sulfur density ratio. For all ion species we find the brightness peaks around 5.7 RJ.

By comparing the observed brightness ratios of various spectral lines to that predicted by the CHIANTI atomic physics database we derive a radial profile of the electron temperature of the torus. Using this electron temperature profile and a simple, column density-based torus model we obtain estimates for the oxygen and sulfur ion densities in the torus.

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

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