On the problem of polarization characteristics of radio waves in a randomly inhomogeneous magnetoactive plasma

Expressions for the Stokes parameters when radio waves propagate in a turbulent magnetoactive plasma have been obtained using a refractive scattering method. The problem of the spatial coherence of polarized radiation is considered. Expressions for the correlation functions and fluctuation dispersions of the Stokes parameters are found in the case of saturated wave field fluctuation. It is shown that the fluctuation of the circular polarized component will be observed in the received radiation even if the circular polarization is absent in the radiation that is incident on the magnetoactive plasma slab. A method is proposed to define the preference orientation of the magnetic field in the inhomogeneous layer of space plasma, which is biased on the simultaneous measurement of the space correlation functions of the I, V Stokes parameter fluctuation and Faraday rotation of the radiation polarization plane from the source with known polarization characteristics.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Radiofizika, Vol. 39, No. 8, pp. 1007–1013, August, 1996.This work was supported in part by the Russian Foundation for Fundamental Research under Project No. 96-02-18632.     

Quantum Polarization Characteristic Function and Cumulant Analysis of Stokes Parameters

We derive the unitary polarization operator for the so-called lowering and raising operators in the factorized form and, based on this operator, determine characteristic functions and calculate cumulants for the single-mode coherent radiation, two-mode entangled states, and polarization-squeezed light. Higher-order cumulants clearly show the non-Gaussian statistics of the Stokes parameter fluctuations and the connection between them.

     

Stokes Flows under Random Boundary Velocity Excitations

A viscous Stokes flow over a disc under random fluctuations of the velocity on the boundary is studied. We give exact Karhunen-Loève (K-L) expansions for the velocity components, pressure, stress, and vorticity, and the series representations for the corresponding correlation tensors. Both the white noise fluctuations, and general homogeneous random excitations of the velocities prescribed on the boundary are studied. We analyze the decay of correlation functions in angular and radial directions, both for exterior and interior Stokes problems. Numerical experiments show the fast convergence of the K-L expansions. The results indicate that ignoring the stochastic fluctuations in boundary conditions dramatically underestimates the variance of the velocity and pressure in the interior/exterior of the domain. The support of the RFBR Grant N 06-01-00498 is kindly acknowledged.     

Scattering losses from planar waveguides with material inhomogeneity

Abstract

We consider the propagation of guided waves in a planar waveguide that has a finite-length segment of inhomogeneous media. Except for the inhomogeneous segment, which varies in length from 0 to 160λ, the waveguide is piecewise homogeneous everywhere. The inhomogeneity is modelled by two-dimensional random permittivity fluctuations that are numerically generated from an assumed Gaussian correlation function.

In 2D, the Maxwell equations are solved in the frequency domain for both TE and TM polarization by using modal expansion methods, perfectly matched absorbing boundary layers and the R -matrix transfer matrix algorithm. The guided waves are excited by a Gaussian beam incident on the waveguide aperture. For various waveguide design parameters, numerical results are given for waveguide power loss per unit length of waveguide inhomogeneity. The power loss curves are calculated as the average from numerous realizations of the random permittivity and the coefficient of variation is also given.     

Polarization transfer in media with nongaussian random inhomogeneities

The matrix equation of transfer of averaged polarization properties — the Stokes mean parameters in a statistically inhomogeneous, weakly magnetized plasma with chaotic variations in orientation of an external magnetic field distributed by Poisson law — is derived in the range of quasi-longitudinal propagation. Its analytical solution allows us to estimate an effective chaotization scale of radiation polarization in such media.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Radiofizika, Vol. 39, No. 3, pp. 335–342, March, 1996.     

Scattering losses from planar waveguides with material inhomogeneity

We consider the propagation of guided waves in a planar waveguide that has a finite-length segment of inhomogeneous media. Except for the inhomogeneous segment, which varies in length from 0 to 160λ, the waveguide is piecewise homogeneous everywhere. The inhomogeneity is modelled by two-dimensional random permittivity fluctuations that are numerically generated from an assumed Gaussian correlation function.

In 2D, the Maxwell equations are solved in the frequency domain for both TE and TM polarization by using modal expansion methods, perfectly matched absorbing boundary layers and the R-matrix transfer matrix algorithm. The guided waves are excited by a Gaussian beam incident on the waveguide aperture. For various waveguide design parameters, numerical results are given for waveguide power loss per unit length of waveguide inhomogeneity. The power loss curves are calculated as the average from numerous realizations of the random permittivity and the coefficient of variation is also given.     

On the scintillations of radiation from an extended source in a randomly inhomogeneous medium

Using the method of refractive scattering of radio waves (RSRW), we solve the problem of space correlation of scintillations of radiation from an extended source in a randomly inhomogeneous medium. General expressions are obtained for the index and radius of the space correlation of fluctuations of intensity of radiation from a source with finite angular dimensions as it propagates though a multilayered medium with refractive index fluctuations. The RSRW method is similar to the diffraction calculation of space correlation of scintillations of an extended source in a thick layer with inhomogeneities. We note that under certain conditions an increase in the number of inhomogeneous layers on the radio wave propagation path leads to a pronounced decrease in the scintillation index and an increase in the space correlation of fluctuations of intensity of received radiation from an extended source. The results obtained have a simple geometric-optical interpretation. We indicate a specific feature in determining the angular dimensions of extended radio sources using the known method of scintillations. Radiophysical Research Institute, Nizhny Novgorod, Russia. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Radiofizika, Vol. 40, No. 5, pp. 586–593, May, 1997.     

Propagation effects in the radio interferometry of polarized radiation: II. Fluctuations of polarized radiation in a random magnetoplasma

This paper analyses fourth-order moments of polarized radiation passing through magnetoactive plasma with random irregularities both in electron density and in magnetic field. We consider the new propagation effect arising from chiral properties of random magnetoplasma. That is, the lens formed by the same irregularities of magnetic field may be characterized by refractive properties of opposite sense vis-a-vis the rotation of the wave polarization vector. This produces an appearance of slight circular polarization fluctuations arising from initially nonpolarized radiation. Analysis of the polarized radiation fluctuations may allow the spatial spectrum of magnetic field irregularities to be detected. The enhanced level of the circularly polarized component, and the share of fluctuations owing to magnetic field irregularities, can be readily observed at low frequencies only, say, in the radiation passing through the solar chromosphere or the Jovian and terrestrial ionosphere, (magnetosphere).     

Changes in statistics of the instantaneous Stokes parameters of a quasi-monochromatic electromagnetic beam on propagation

The changes in the probability density functions (PDFs) are discussed, of the instantaneous Stokes parameters of a quasi-monochromatic electromagnetic beam propagating in free space. Such changes may be caused by correlations between the components of the electric field at a pair of points in the source plane. When the fluctuations of the electric field are governed by Gaussian statistics the PDFs of the instantaneous Stokes parameters at any distance from the source are completely determined by the two-point correlation properties of the field in the source plane. These results can be used for synthesis of sources generating random beams with prescribed statistical properties. They also may find applications in remote sensing, tomography and communications with partially coherent and partially polarized light.     

On the Effect of Small-Angle Scattering by Density Fluctuations on the Efficiency of Linear Transformation of Ordinary and Extraordinary Waves in a Toroidally Inhomogeneous Plasma

We have analyzed the efficiency of tunneling of quasi-optical wave beams through the evanescent region in the vicinity of plasma cutoff in a randomly inhomogeneous magnetoactive plasma. A new theoretical model proposed here makes it possible to study the effect of a random phase modulation induced by density fluctuations in the wave beam path on the efficiency of the linear transformation of waves in the 2D geometry corresponding to the experimental conditions for heating the overdense plasma in toroidal magnetic systems. We have derived a general analytic expression connecting the wave beam coefficient of transformation averaged over the ensemble of random wave field realizations with its phase correlation function. We have analyzed the dependence of the coefficient of transformation on the correlation length for the random phase distribution in the beam and on the traversed path length to the interaction region. The threshold value of the path length above which the fluctuations produce a dominating effect has been determined. The importance of taking into account the 2D effects has been demonstrated.     

Nonclassical polarization properties of fundamental radiation in the case of generation of the second optical harmonic by mixing

The evolution of quantum fluctuations of the quadrature components, the number of photons and the Stokes parameters of fundamental radiation that excites the second harmonic in interaction of type II is considered. Special attention is given to the variances of the Stokes parameters of the fundamental radiation. It is shown that the fluctuations of three Stokes parameters decrease and those of the fourth Stokes parameter increase in comparison with the fluctuations for the case of coherent radiation.     

在与原子相互作用中光偏振态的量子描述及其演化

应用偏振光的量子理论和斯托克斯算符研究了无克尔媒质和存在克尔媒质情况下，光在与原子相互作用过程中偏振态的演化.研究了偏振光中斯托克斯参量的涨落及其压缩的非经典行为.偏振椭圆、量子光学中的偏振度和斯托克斯参量的信噪比也得到了讨论.结果表明斯托克斯参量及其涨落在时间演化中呈现出被调制的振荡，这些振荡表现出间歇地崩塌和恢复.在与原子的相互作用过程中，光的偏振椭圆不随时间变化，但偏振度却随时间出现振荡.克尔媒质对这些振荡演化有很大影响. 关键词： 斯托克斯算符 斯托克斯参量 量子偏振态 量子涨落     

Fluctuations in the relativistic quantum plasma

The fluctuations of various parameters of the relativistic quantum plasma are studied with the use of the covariant Wigner function techniques. The fluctuations of the covariant Wigner function of the ideal Fermi gas at thermal equilibrium are calculated. The result is a function of the one particle Wigner function and the anticommutator of the Dirac fields only. As a consequence second order correlation functions of the four-current and the momentum-energy tensor are obtained and analyzed. On the basis of the fluctuation-dissipation theorem, the polarization tensors at first order in e² of the magnetized and the non-magnetized electron gas are derived from the four-current fluctuations of the ideal plasma. Expressions are given for the magnetized vacuum polarization in two representations, integral and discrete sums over Landau levels, for arbitrary values of the photon four-momentum. The dispersion relations of the magnetized gas are studied in the limit of low frequencies and wavenumbers. It is shown that owing to relativistic quantum effects, the characteristic frequencies of the plasma modes (plasma and Larmor frequencies) split into effective transverse and longitudinal frequencies. The existence of an acoustic mode (zero sound) for the one-component plasma is also shown.     

The moon as a cosmic source of linearly polarized radio emission

We analyze parameters of the partially linearly polarized thermal radio emission from the Moon taking the effects of radiative heat transfer and surface roughness into account. The distributions of the Stokes parameters I, Q, and U over the visible lunar disk are considered. The polarization parameters of the integral radio emission as functions of the frequency and the Moon phase are obtained by integrating the Q and U distributions. We consider the possibility of using the Moon as a reference source of partially linearly polarized radiation for space-borne and ground-based projects aimed at studying polarization of the Galactic radio emission and the cosmic microwave background. __________ Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Radiofizika, Vol. 50, No. 7, pp. 593–606, July 2007.     

Collisional change in the polarization characteristics of an ensemble of excited Ti(XXI) ions in a plasma

Collisional change in the polarization characteristics of an ensemble of excited ions whose lifetime is much shorter than the average collision time is considered. The obtained dependences of the Stokes parameter on the ion drift velocity make it possible to perform diagnostics of the plasma parameters by the polarization characteristics of radiation.     

Stokes parameters and polarization contrasts in Young's interference experiment

We derive a spectral interference law that governs the behavior of the four Stokes parameters in Young's two-pinhole experiment with a random electromagnetic beam. In addition to the visibility of intensity fringes, we introduce three new contrast parameters that describe the interference-induced changes in the field's state of partial polarization. The polarization modulation depends on the electric field correlations at the pinholes and is closely related to the two-point Stokes parameters. The results are expected to be particularly useful in polarization interferometry and electromagnetic coherence theory. The formalism is demonstrated with specific examples.     

Intensity fluctuations in a moving random medium

We consider the intensity fluctuations arising when a point source of radiation moves in a randomly inhomogeneous scattering medium. The medium itself can also move with a velocity whose component normal to the direction of propagation can have an arbitrary distribution. We derive an expression for the space–time autocorrelation function of the intensity fluctuations transverse to the direction of propagation. The result is analysed for some particular cases and it is shown how the resulting information can be useful in examining the behaviour of random media in situations of practical interest.