MEIM Model: Differentiating Ring Current And Radiation Belt Contributions to Inner Magnetospheric Phase Space Density

The Middle Energy Inner Magnetosphere (MEIM) model is an inner magnetospheric phase space density model based on thermodynamic parameters derived from fitting of the Van Allen Probes RBSPICE ion data. A strong positive trend between the percentage of fits below the error threshold and L-shell (in Earth radii) was found, along with a distinct topological difference between the bins on the equator ([-5,5) degrees magnetic latitude) compared to the bins below ([-20,-5) degrees magnetic latitude) and above ([5,20) degrees magnetic latitude) the equator. The Dst dependence was found to be more pronounced in the off-equatorial bins, as well. This result is believed to be partially attributable to the radiation belt proton population being co-located in phase space with the ring current population at lower L-shells, with the ring current being a significantly more anisotropic population than the phase-space co-located radiation belt protons. Counting statistics for energy channels in the co-located phase space region feature both Poisson and non-Poisson counting statistics, which is also indicative of multiple processes being present. We anticipate further analysis of the counting statistics enabling the appropriate two-population fitting necessary to accurately recover the thermodynamics of the radiation belt population and subsequently include this second population into the MEIM framework.