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W.H. Smyth (Atmospheric and Environmental Research, Inc.), M.L. Marconi (Fresh Pond Research Inst.)
Three-dimensional calculations for the Iogenic plasma source (pickup ion rates produced from Io’s atmosphere by electron and charge exchange processes in the plasma torus) have been undertaken for its spatial distribution both on a circumplanetary scale and a near-Io scale as created by O and S gases located above Io's exobase in its corona and escaping extended neutral clouds (designated as the “Outer Region” source). These calculations have been performed using the AER neutral cloud models for O and S with realistic incomplete collisional cascade source strengths and velocity distributions at Io's exobase and realistic spacetime loss processes in the plasma torus. On the circumplanetary spatial scale, the instantaneous Iogenic plasma source is highly peaked about Io's position on its orbit around Jupiter. The spatial distributions of a number of physical quantities such as the total and net-mass loading rates, the pickup ion density, the pickup conductivity, the pickup current, and the net-energy loading rate are determined for the “Outer Region” sources. By comparison of the “Outer Region” source rates with other independent estimates for the total Iogenic plasma source rates contained within Io’s Lagrange sphere radius (5.81 Io radii), the relative importance of the Iogenic plasma source created by the “Inner Region” (spatial region below Io’s exobase) is estimated. Within the Lagrange sphere, the Iogenic plasma source for the “Inner Region” dominates that for the “Outer Region” by an order of magnitude or more. By combining the “Inner Region” and “Outer Region” estimates, a picture for the Iogenic plasma source from above Io’s surface to throughout the complete plasma torus volume is established. This overview picture and the spatial behavior of select pickup quantities near Io will be presented. The work was supported by the NASA Planetary Atmospheres and Jupiter System Data Analysis Programs.
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Bulletin of the American Astronomical Society, 34, #3< br> © 2002. The American Astronomical Soceity.