3D Multi-fluid Simulations With Ion-Neutral Interactions: Combining Observations and Modeling to Study Enceladus' Plume

The Cassini spacecraft discovered a plume of water ice particles jetting outward from the southern polar region of Saturn's moon Enceladus. Preliminary modeling studies in conjunction with Cassini spacecraft observations have demonstrated the presence of an extended source of ions likely due to charge exchange and ion production in the expanding neutral plume. While the importance of understanding the chemical interactions in this system has been recognized, a self-consistent model examining the neutral and ion dynamics and their interaction has yet to be fully established. In this paper we present results from incorporating neutral fluid components and ion-neutral interactions into an existing multi-fluid modeling infrastructure. The ion and neutral fluids interact through charge exchange, and the production and loss of ions and neutrals are monitored through source and loss terms in each fluid species in each grid cell. The model is used to interpret Cassini spacecraft observations from the July 2005 encounter, the result of which strongly indicates that treating both ions and neutrals consistently throughout a multi-fluid plasma dynamic model is necessary to fully understand the local and extended interaction of Enceladus" plume with Saturn's magnetosphere. Improved understanding of ion-neutral interactions can later be implemented for tracking the numerous sources of neutrals and ions within Saturn's magnetosphere, such as the neutral atmosphere of the rings, icy moons, and Titan.