HR: 1340h
AN: SM13B-0336    [Abstracts]
TI: Modeling Spatial and Temporal Variability of Plasma in the Io Plasma Torus
AU: * Bagenal, F
EM: bagenal@colorado.edu
AF: University of Colorado, Laboratory for Atmospheric and Space Physics CB 392 Duane Physics D133 University of Colorado , Boulder, CO 80309 United States
AU: Delamere, P
EM: delamere@lasp.colorado.edu
AF: University of Colorado, Laboratory for Atmospheric and Space Physics CB 392 Duane Physics D133 University of Colorado , Boulder, CO 80309 United States
AB: A model of the physical chemistry of the Io plasma torus (Delamere and Bagenal, JGR, 108, A7, 2003) has been adapted to include spatial variations in plasma conditions with latitude, radial distance and longitude. To model plasma conditions observed by the Cassini UVIS instruments Io needs to produce 700-1200 kg/s of neutral sulfur and oxygen atoms. Approximately 50% of these neutrals charge-exchange with singly-ionized sulfur or oxygen ions resulting in the loss of fast neutrals, the addition of pick-up energy to the plasma but no increase in ionization. The average net addition of charge to the system is roughly 1.5 × 10²⁸ electrons/s. Radial transport time scales of 40-60 days are consistent with earlier studies of the torus. The observed 1.4 TW power emitted by the torus in the UV requires an addition of energy from suprathermal electrons (which are modeled as a fixed fraction of 0.25% at a temperature of 45 eV). At different epochs the torus conditions (density, temperature, composition, radiative output) varied between Voyager flybys and Galileo orbits. Such variations can be modeled by changing the neutral source, transport time and hot electrons of a steady-state torus. Short-term variability of torus emissions on the time scales of 10s of days (as observed by Cassini on its approach to Jupiter) have been modeled with a time-dependent model with a simple gaussian increase in neutral production and proportional decrease in transport time scale.
DE: 2732 Magnetosphere interactions with satellites and rings
DE: 2756 Planetary magnetospheres (5443, 5737, 6033)
DE: 5719 Interactions with particles and fields
DE: 5780 Tori and exospheres
DE: 6219 Io
SC: SPA-Magnetospheric Physics [SM]
MN: Fall Meeting 2005