Charon's Impact on the Pluto-Solar Wind Interaction

This work studies Charon's effects on the Pluto-solar wind interaction using a multifluid MHD model which simulates the interactions of Pluto and Charon with the solar wind and each other. Specifically, it investigates the magnetospheric dynamics of a two body system in which either one or both bodies posses an ionosphere. In order to more accurately capture the behavior of the Pluto-Charon system, ion-neutral interactions, including source and loss processes, have been incorporated into the model. Ion-neutral interactions are important due to the highly extended atmosphere in the system, with pick up ions having been detected several million kilometers upstream of the system by the PEPSSI instrument aboard New Horizons. In order to more fully characterize the system, simulations with various system geometries have been performed, in which Charon's position relative to Pluto varies. In addition to the New Horizons system encounter geometry, simulations in which Charon is directly upstream and directly downstream of Pluto are considered. Depending on the bow shock stand-off distance upstream of Pluto, Charon could periodically pass outside of the shock. The results of this study demonstrate that in these circumstances Charon modifies the upstream flow, both in the case in which Charon possesses an ionosphere, and in the case in which Charon is without an ionosphere.