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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[17.09] Evolution of the Io Plasma Torus over One Week

J. W. Weiss, N. M. Schneider (Univ. of Colorado/LASP)

The physical parameters of density and temperature in the Io plasma torus are of great interest to studies of mass and energy movements in the torus. Unfortunately, these quantities are difficult to obtain from ground-based images due to line of sight effects. In situ spacecraft measurements are rare in space and in time, so provide only a glimpses of the torus's behavior.

We provide a method to determine these parameters by modeling the three-dimensional torus with the Colorado Io Torus Emission Package (Martin Taylor, Ph.D. thesis). By fitting models to ground-based data, we recover densities and temperatures at the limb of the torus. In the ribbon, find significant variations in temperature (a factor of 8) and in density (a factor of 3) over the longitudes of the torus in one night, in agreement with Schneider and Trauger (ApJ, vol. 450, pp 450-462). Furthermore, we find variations in torus structure from night to night. In particular, there is evidence of localized heating of the torus from one night to subsequent nights over the course of the week's data, with the warmed region of the torus appearing to super-corotate. Implications of this heating might include the introduction of a superthermal ion population into the torus (Smith et al., GRL, vol. 15, pp 545-548). We evaluate the number of hot ions needed to heat the torus as well as the heating time.

This work is supported by NASA's Planetary Astronomy Program.

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

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