Fluctuations in the amplitude of a wave upon mutual diffusion of rays in a medium with random inhomogeneities

Fluctuations in the plane-wave amplitude and positions of two rays that propagate in a medium with random inhomogeneities of dielectric permittivity are considered. The solution to the problem is based on the ray-diffusion method. The Einstein-Fokker equation is obtained for the density of probabilities of the distance between the rays and relative amplitude in the case where the initial distance between the rays is much smaller than the correlation radius of dielectric permittivity. A conditional probability density for the relative amplitude is obtained provided that the distribution of distances between the rays is described by a logarithmic normal law, which does not take amplitude fluctuations into account. Numerical analysis of the analytical solution is carried out for the propagation of short radio waves in the troposphere and ionosphere.     

On the probability distribution for rays in a medium having random inhomogeneities

Radiophysics and Quantum Electronics -     

A study of the fluctuations of ray positions during mutual diffusion in a medium with random inhomogeneities

Fluctuations in the positions of two rays propagating in a medium with random permittivity inhomogeneities are considered. The problem solution is based on the ray diffusion method. The density of probabilities for the difference in ray positions is obtained for the case when the initial distance between the rays is much smaller than the correlation radius of permittivity fluctuations.     

Signal propagation in two-layer medium with random large-scale inhomogeneities

A formula is derived for the average intensity of a signal propagated in a medium with a semitransparent layer and random large-scale inhomogeneities. A solution is obtained by the interference-integral method and the resulting formula is represented as an integral with respect to the sines of the partial-wave exit angles. The case in which the emitted pulse has a Gaussian form is examined as an example. Results of numerical modeling of the average signal intensity and the width of the semitransparency frequency band are given.Institute of Applied Physics at Irkutsk State University. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Radiofizika, Vol. 36, No. 6, pp. 475–483, June, 1993.     

Vector statistics of multiply scattered light in a random medium with large inhomogeneities

The distribution function of the scattered radiation intensity is calculated in the approximation of the basic polarization modes. In such an approximation, the distribution function is represented in terms of the degree of polarization of the initially circularly and linearly polarized waves transmitted by the sample. The effect of the difference of the decay rates for the circular and linear polarization modes on the statistics of the light waves that are multiply scattered in the medium with large inhomogeneities is analyzed.     

Aberrations in materials with random inhomogeneities

Materials that consist of a random microstructure can affect ultrasonic measurements--reducing signal strength, increasing noise, and reducing measurement accuracy--through scattering and aberration of the acoustic field. To account for these adverse effects a phase screen model, alongside the stochastic wave equation, has been developed. This approach allows the field and study aberrations to be modeled from a statistical point of view. Experimental evidence of aberration and statistical properties of the measured acoustic field are shown. A measured correlation function of the acoustic field is interlinked to mean crystallite size by using a theoretical coherence function that can be mainly described by the correlation length and wave velocity variation of microstructure. The estimation of the mean crystallite size using this technique would provide some insight into material characterization.