Research Article

Ionospheric scintillation modeling. I. Validity of the plane wave approximation for an electromagnetic wave illuminating the ionosphere

¹ DEMR, ONERA, Université de Toulouse, 31000 Toulouse, France
² DEMR, ONERA, 13330 Salon-de-Provence, France

^* Corresponding author: gregory.morel@onera.fr

Received: 23 April 2025
Accepted: 16 October 2025

Abstract

Low Earth Orbit (LEO) satellites have a low altitude orbital track around the Earth. For a satellite to Earth link passing through the ionosphere, the approximation of the electromagnetic wave illuminating the ionosphere irregularities by a plane wave is questionable. We develop an analytical method for quantifying the error induced by the formalism assuming an incident plane wave illuminating a turbulent ionospheric layer. The method is applied to the special case of weak scattering under a thin-layer assumption. It is validated through comparison with the numerical approach solving the Parabolic Wave Equation (PWE) associated with Multiple Curved Phase Screens (MCPS). In addition, the correction of the classical incident plane wave approach by correcting the Fresnel distance from plane wave to spherical wave is considered. The analytic method allows quantifying the errors induced by an incident plane wave approximation or by the approach using the corrected Fresnel distance. For this, the amplitude and phase scintillation indices, respectively S₄ and σ_φ, are compared when the transmitter – irregularities distance varies. Finally, in realistic configurations, the impact of satellite altitude on ionospheric scintillation is computed and discussed.