Analysis of chemistry models for DSMC simulations of the atmosphere of Io

In order to study the planetary atmosphere of Io, a moon of Jupiter, the chemical reaction rate between SO ₂ and O obtained using the Molecular Dynamic/Quasi-Classical Trajectory (MD/QCT) method are compared with other sources and the Total Collisional Energy (TCE) model of Bird. The MD/QCT calculations are found to result in lower rate constants and reaction probabilities than the TCE model in the temperature range of 6,000 K and above and also reveal the vibrational favoring feature of the reaction SO ₂ + O → SO + 2O. The implementation of both MD/QCT and TCE chemistry reaction models in DSMC is examined through the analysis of the 0-D time dependant and 2-D axi-symmetric DSMC simulations. The difference between the MD/QCT and TCE models is observed in the reaction product contours in the 2-D problem. The lower rate constant and reaction probability predicted by the MD/QCT model compared to the TCE model creates a smaller reaction region in the 2-D axi-symmetric simulation, lower product concentration, and higher temperature. In addition, the reaction region is found to be highly non-equilibrium, which suggests that MD/QCT is a more suitable model for the simulation of the Io's atmosphere.