Modelling of Earth's ionosphere F layer. Solution of the ambipolar diffusion equations

The paper presents the problem formulation and methods of numerical solution for the global dynamical model of Earth's ionosphere F layer (altitude 100–500 km), which is a computational unit of the coupled thermosphere-ionosphere model. The model is based on a set of equations of global ionospheric formation and dynamics in a spherical geomagnetic coordinate system in the approximation of a thin spherical layer. The features of the formulated equations are investigated and methods for its solution are proposed based on the splitting method. In this paper we present the results of the first stage of the splitting method — solution of equations describing the ambipolar diffusion along magnetic field lines and gravitational settling of ions as well as plasma chemical transformations. Based on the prescribed analytical solution, which qualitatively describes the real ionospheric electrons distribution, the accuracy of the proposed algorithms is investigated. We also presents the results of numerical study for the sensitivity of solution to perturbations of the ion flow at the upper boundary.