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M. L. Marconi (The Freshpond Research Institute), M. C. Wong, W. H. Smyth (Atmospheric and Environmental Research Inc.)
A Hybrid Fluid/Kinetic Model of Io's Atmosphere (Preliminary Results)
Io posseses a unique and complex atmosphere with important effects on the Jovian magnetosphere. The atmosphere derives from a highly asymmetric SO2 source which is bombarded by the dense heavy ion strongly magnetized sub-Alfvenic plasma of the Io plasma torus. This results in a tremendous chemical and dynamic transformation of the SO2 atmosphere into a highly nonthermal distribution of O and S with the newly ionized neutrals such as S+ and O+ ultimately sustaining the plasma torus and making Io the principal source of heavy ions in the Jovian Magnetosphere. In addition, the currents generated in this atmosphere/plasma torus interaction are strong enough to strongly perturb the plasma flow near Io and cause aurorae on Jupiter.
Modeling of this complex atmosphere has up to now been accomplished with either fluid/diffusion chemical models (Wong and Johnson 1996 and Summers and Strobel 1996, for example) for the lower levels of Io's atmosphere and purely exospheric models (Smyth and Combi 1988) which are for the collisionless distant regions of the atmosphere. However, as indicated by Marconi et al (1996), Io's atmosphere consists of 3 coupled regions, hydrodynamic, transitional, and exospheric.The transitional flow region, where collisions are important but not frequent enough to thermalize the atmosphere, has been more or less neglected up to now. For Io, however, this region is of particular importance since much of the intense plasma/atmosphere interaction takes place here. We present preliminary results from a new 2 dimensional multi-species version for Io of the hybrid fluid/kinetic model of Marconi et al. specifically designed to consistently treat all of the above flow regions.
Marconi, M.L., L. Dagum, and W.H. Smyth, Ap.J. 469, 393, 1996.
Smyth, W.H. and Combi, M.R., ApJ. Supp. 66, 397, 1988.
Summers, M.E. and D.F. Strobel, Icarus 120, 290, 1996.
Wong, M.C. and R.E. Johnson, JGR 101, 23243, 1996.