The study is focused on numerical modeling of vertical ionograms in horizontally non-stratified ionosphere. We have considered the F2-layer ionospheric disturbance shifted horizontally from the sounding point. The presence of this kind of disturbance is related to off-vertical reflections and, hence, multipath propagation. We have investigated the ionogram additional trace that is formed due to off-vertical ray paths. Variations in the disturbance amplitude and related changes in the shape of additional trace have been considered. Typical ray paths are presented that form additional traces in the ionogram.
The paper describes propagation of radio waves in cosine ionospheric layer. It is shown that similar to parabolic layer, analytical solution of ray equations for the cosine layer is possible through special functions. In this case, the advantage of the model in question against the parabolic layer is that there are no gaps in the electron density derivative with respect to coordinate.
The problem of electromagnetic-wave propagation in anisotropic plasma cannot usually be described by exact analytical solutions even in simplest model cases. One of main approximate methods is a geometric optics which provides an illustrative description of radio wave propagation in terms of ray paths [1]. Applicability boundaries of the method (wavelength is smaller than the typical scales of the medium) generally work quite well in the problem of ionospheric propagation of radio waves. Isotropic approximation, i.e. neglect the effect of the Earth's magnetic field, is widely used to simplify the ray-optical description of ionospheric propagation of radio waves. In particular, the advantage of this approach is that for a set of ionospheric models it allows to obtain analytical solutions for the parameters of the ray path. It has been extensively discussed in the literature that the isotropic approximation works quite well for ionospheric sounding being representative of the ordinary mode.
We study variation in the ionogram trace at a change in the propagation range. Addressed are the signatures of traveling ionospheric disturbances on ionograms.
Isotropic approximation, i.e. neglect of magnetic field effects, is widely used to simplify the geometrical optics description of ionospheric propagation of radio waves. However, this description under certain conditions may produce a significant error. In this study, ray traycing is performed to examine an isotropic approximation error in relation to operating frequency and radiation angles.
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