Knowledge of the cold plasma mass density is critically important for a number of magnetospheric studies in the inner magnetosphere. For instance models of the mass density are important for radiation belt research, magnetohydrodynamic models of the solar wind and magnetosphere interaction and Ultra Low Frequency wave research. This is a very difficult quantity to observe directly so an indirect approach will be used. This approach makes use of Alfvén wave resonances. The research will expand on previous determinations of the mass density by extending the results closer to the Earth (L~2) and providing a 3D model. The resulting density model will be parameterized by location, solar wind and geomagnetic conditions. This improvement in our knowledge of the mass density will result because of new data from the THEMIS mission.
The strength of this proposal is that it will address a great need for mass density models that extends beyond the present study. If the only accomplishment of this study is expanded radial coverage of the density models it will be a success and that is highly probable.
