A Sensitivity Study of the Enceladus Torus Chemistry

We have developed a homogeneous cubic centimeter chemistry model to investigate the Enceladus torus. Electron impact dissociation/ionization, electron recombination, charge exchange (including dissociative exchanges), and photodissociation/photoionization are included. The mass source is neutral H2O, and energy is input from pickup of ionized neutrals by the magnetosphere. Mass and energy losses are due to ion radial diffusion, radiation, and escaping hot neutrals produced by charge exchange and recombination. In addition, we have performed a sensitivity study involving the following: hot electron (1) temperature and (2) population fraction (neh/nec), (3) ion radial diffusion timescale, (4) neutral source rate, and (5) dilution of equatorial protons caused by the ambipolar potential. Parameter combinations are chosen so that model output most closely matches Cassini data for: (1) electron density [RPWS, Persoon et al. (2006)], (2) core electron temperature [CAPS-ELS, Lewis et al. (2008)], and (3) on the mixing ratio of water group ions to protons (W+/H+) [CAPS, Williams (2008)] . Note that this set of constraints is arbitrary. Parameter ranges consistent with these constraints will be presented.