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J.V. Austin, D.B. Goldstein (Univ. of Texas)
Atmospheric flows produced by volcanic SO2 plumes on Io are modeled using the direct simulation Monte Carlo (DSMC) method, a rarefied gas computational technique. The plumes are supersonic and exhaust vertically into a uniform gravitational field. The flows are mostly rarefied with continuum conditions existing only in the plume core. Io's surface is modeled as a variable temperature boundary where the sublimation and condensation rates are varied. In the resulting flows two shocks are observed; a hemispherical canopy shock located above the plume and a re-entry shock located near the ground.
Heating due to neutral plasma bombardment and cooling by non-LTE radiation are modeled. Quantities of a second, non-condensible gas are also added to simulate the possible effects of H2S or O2 in the atmosphere. The DSMC code written for this effort accurately models multiple species, rarefied/continuum transition, rotational internal energy, sublimation and condensation, plasma bombardment heating, and non-LTE radiative heat transfer.
The ratio of non-condensible background gas pressure to plume SO2 mass flow rate is varied and the effect on SO2 transport is studied. Different size and strength plumes are modeled to simulate several observed volcanos. Sensitivity of the results to the surface boundary condition is analyzed. The results the used to calculate dynamic pressures which may be encountered by Galileo during the GEM plume fly-thru.
This work has been supported by NASA's Planetary Atmospheres Program.
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