Comparing Different Approaches of Modeling Magnetospheric Composition

The magnetosphere contains a significant amount of ionospheric O+, particularly during geomagnetically active times. The presence of this ionospheric plasma has a notable impact on magnetospheric composition and processes. There currently exist only a handful of approaches to model magnetospheric composition: multi-fluid MHD, multi-species MHD, and individual particle tracing techniques. We present an overview of the advantages and disadvantages of these different approaches and provide a direct comparison of their results. Details of the new multi-fluid and multi-species MHD versions of the BATS-R-US model of the magnetosphere are given. The multi-fluid and multi-species MHD approaches are directly compared for May 4, 1998 and March 31, 2001 geomagnetic storms. These approaches yield comparable results, namely a more strongly negative Dst, reduced CPCP, and a drastically improved magnetic field at geosynchronous orbit, as compared to single-fluid MHD with no ionospheric outflow. We also simulate the October 2002 geomagnetic storm and directly compare our multi-fluid and multi-species simulations to the particle tracing approach used by Fok et al, [2008].