Galileo Observations of the Io Plasma Torus

Tuesday, 16 December 2014
Edward Gregory Nerney, University of Colorado at Boulder, Boulder, CO, United States, Fran Bagenal, Univ Colorado, Boulder, CO, United States, Wayne Robert Pryor, Central Arizona College, Coolidge, AZ, United States and Andrew J Steffl, Southwest Research Institute, Boulder, CO, United States
We present a survey of conditions observed in the Io plasma torus throughout the Galileo mission (1995 to 2003). This Galileo epoch includes the time of the Cassini flyby of Jupiter (fall 2000 to spring 2001) when the UVIS instrument made extensive observations of the spatial and temporal variations of torus emissions (Steffl et al. 2004, 2006). We compare re-analyzed Galileo EUV observations of torus emissions with a physical chemistry model based on Delamere et al. (2004) to derive modest variations in torus model parameters (transport time, neutral source, population of hot electrons, ratio of neutral oxygen to sulfur atoms in the source) over the Galileo era. Torus plasma conditions derived from these emissions are also compared with in situ measurements by the Galileo PLS and PWS instruments as well as the Cassini UVIS observations and ground-based observations of torus emissions.