Data Assimilation using 4D-Var for the Radiation Belt Environment

The Earth's radiation belts experience significant and abrupt changes due to acceleration, loss, and transport processes of the trapped energetic electrons in Earth's magnetic field. Since high-energy particles can potentially damage space infrastructure, understanding and predicting the dynamics of the radiation belts is of particular importance. In this work we implement a four dimensional variational data assimilation (4D-Var) to a radial diffusion equation and its parameterizations modeling the radiation belt environment. Specifically, we use the 4D-Var to determine transport coefficients (DLL, and τ) within the model that control how particles are distributed throughout Earth's magnetic environment. A series of assimilation experiments are perform to not only estimate the correct radiation belt environment, but also estimate the appropriate value of the various parameterization commonly used in the models. The results are compared with other assimilation techniques to assess the effectiveness of the 4D-Var for this problem.