Analysis of plane wave approximation for an electromagnetic wave illuminating an inhomogeneous ionosphere layer

The influence of the approximation of the electromagnetic wave illuminating an inhomogeneous ionospheric layer to a plane wave in the modeling of ionospheric scintillation is here studied theoretically. Indeed, Low Earth Orbit (LEO) satellites have an orbital track around the Earth passing through the ionosphere so that the plane wave assumption conditions are not met and the sphericity of the electromagnetic wave propagating through the ionosphere before being scattered towards the ground should be considered. Thus, this work proposes a quantification of the error induced by the incident plane wave model. The approach commonly used for modeling the propagation of an electromagnetic wave is the Rytov's theory of weak scattering which allows to derive analytic and asymptotic formulations of the electromagnetic field moments. These results are useful to study the impact of satellite altitude above ionosphere layer on scintillation.