MLT-Dependent 3D Reanalysis of Radiation Belt Elections: Quantifying Errors in Current and Future Magnetic Field Models
Tuesday, 16 December 2014
Earth's electron radiation belt dynamics are highly dependent on the state and evolution of the local and global magnetic field. Spacecraft observations provide sparce information on the current state of the radiation belts, however, together with physics-based modeling they may help to resolve the physical processes at work. The Versatile Electron Radiation Belt (VERB) model solves the Fokker-Planck equation in three dimensional invariant coordinates and includes parameterizations of multiple wave processes within the Earth's magnetosphere. The invariant formulation allows one to more effectively separate adiabatic and non-adiabatic changes in the radiation belt electron population. The Kalman filter provides a method to assimilate data with a model, while taking into account the errors associated with each parameter. A split-operator Kalman filter approach is applied in this study, which provides a fast, and computationally inexpensive tool to assimilate data over very long time periods. Data error estimates are derived through energy-channel-specific intercalibration, while model error estimates are adjusted dynamically based on the model forecast performance. In the current study, the reanalysis is applied to investigate the errors in various magnetic field models; knowledge which is vital for accurate modeling of the radiation belts. The goal of the analysis is to develop a quantitative understanding of the magnetic field model errors, and how they contribute to errors in the invariant coordinates of electron phase space density, namely M, K, and L*. Global reanalysis based on data from different MLT sectors and the current understanding of radiation belt physics, allows one to quickly identify any unphysical characteristics in a comparision between different MLT sectors. Two examples of inaccuracies found thus far are a mis-aligned slot region, and differences in the location and magnitude of PSD at fixed first and second invariants, both of which may be explained by magnetic field model errors. Several older magnetic field models, and the data-derived high-resolution and inner-magnetospheric T07 magnetic field model are applied at selected intervals during the Van Allen Probe mission to quantify their performance at different locations and under various conditions.