Modeling the F Layer of the Earth’s Ionosphere: Solution of the Ambipolar Diffusion Equations

The paper presents the problem formulation and methods of numerical solution for a dynamical global model of the F layer of the Earth’s ionosphere (altitude 100–500 km), which is a computational unit of the coupled thermosphere–ionosphere model. The model is based on a system of equations of the global ionospheric formation and dynamics in a spherical geomagnetic coordinate system in the approximation of a thin spherical layer. The features of the formulated system of equations are investigated and the methods for its solution are proposed based on the method of splitting them by physical processes. In this paper we present the results of a single step of the splitting method—the solution of equations which describe the ambipolar diffusion of ions along the magnetic field lines and the gravitational settling of ions, as well as the plasma–chemical transformations. The accuracy of the proposed algorithms is investigated based on the prescribed analytical solution, which qualitatively correctly describes the real ionospheric electron distribution. The results of the numerical experiments on studying the sensitivity of the solution to perturbations of the ion flow at the upper boundary are provided.