Using previously derived formulas describing wave reflection and scattering in a reflective multiscale inhomogeneous layer, we examine the effect of random irregularities on the sounding signal structure. It is shown that, unlike scattering in a homogeneous medium, scattering by small-scale irregularities in a plane-stratified medium depends on the location of these irregularities relative to the reflection point. This largely determines the scattered pulse structure and the applicability of the geometrical optics approximation to its description
The formulas derived earlier for the frequency coherence of the field of a wave propagating in a layer with a linear profile of mean permittivity are used to simulate the mean intensity of a radio pulse reflected and scattered from a randomly inhomogeneous multiscale ionospheric layer. This intensity is shown to contain a wide pedestal due to backscattering by small-scale irregularities and a pulse with a smaller width determined by broadening of the pulse during propagation in a medium with large-scale irregularities.
The paper deals with multipath effects in ionospheric sounding by radio waves with low-Earth orbiting satellites at frequencies slightly above the critical frequency. The multipath effects in inhomogeneous plasma media are eliminated using an additional spatial field processing. This field processing relies on the Double Weighted Fourier Transform (DWFT). We have carried out numerical calculations for multipath propagation caused by radio wave refraction by plasma defocusing lenses.
The report considers the reflection and scattering of waves in a randomly inhomogeneous multiscale layer. Random irregularities with scales larger and smaller than the wavelength are located in an inhomogeneous deterministic layer with a piecewise linear permittivity profile. The reflected wave field includes waves singly backscattered by small-scale irregularities before or after reflection from a layer with large-scale irregularities. The combination of reflection and backscattering gives rise to two-fold backscattering effects. Asymptotic expressions are given for the frequency coherence function of backscattered wave.
The effect of various ionospheric inhomogeneities on the signal reflected from the ionospheric layer is studied. It is shown that diffraction effects in the vicinity of the reflection point under conditions of a large propagation path are less significant than diffraction effects outside this neighborhood on the propagation path of the radio wave from the source to the reflection point and from the reflection point to the receiver. This not only facilitates the numerical simulation of the vertical sounding signal, but also allows you to increase the resolution of vertical sounding systems by spatial processing of the signal.
This paper studies effects of random anisotropic ionospheric irregularities on the residual error of dual-frequency GNSS measurements. For this purpose, in the phase path equation we take into account second- and third-order corrections associated with geomagnetic effects and ray path bending in the presence of random irregularities respectively. We also examine the influence of the orientation of ionospheric irregularities along geomagnetic field lines (the so-called anisotropy of irregularities) on the third-order residual error of dual-frequency measurements. We simulate the residual error to investigate the conditions under which this effect becomes most significant.
Using a combination of the Fock proper-time method and the double weighted Fourier transform, we have derived a solution of the problem of wave reflection from a regularly inhomogeneous layer with random irregularities. The report uses this solution to determine the mean field and the frequency coherence function. The condition of applicability of the geometrical optics approximation for the frequency coherence function in the narrowband case is much weaker than that for individual realizations. We report the simulation results for the Gaussian spectrum of irregularities and for Shkarofsky's model.
We report the numerical simulation results obtained using a two-frequency coherence function in the double-weighted Fourier transform approximation. We perform the simulation for different models of inhomogeneous media.
The report solves the inverse problem of diagnostics of inhomogeneous plasma through spatial field processing in the form of inverse double weighted Fourier transform (DWFT). As an inhomogeneous medium, we use a model in the form of three Gaussian irregularities. We examine the influence of dimensions of receiving-transmitting aperture system on diagnostic results.
The double weighted Fourier transform method is used to find the average field, scintillation index, mutual coherence function, and intensity correlation in a randomly inhomogeneous multiscale medium. It is noted that the results obtained taking into account second-order effects are consistent with the results obtained with the path-integral method.
We study peculiarities of GNSS phase fluctuations caused by anisotropic irregularities. We have found regions with a higher level of phase variance and analyzed its causes.
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