Temporal Spectrum of a Scattered Electromagnetic Waves in the C…

Collision Turbulent Magnetized Plasma

G. Jandieri1, A. Ishimaru2, B. Rawat3, and N. Tugushi4

1International Space Agency Georgian Society, GTU, Tbilisi, 0160, Georgia

2Department of Electrical and Computer Engineering, University of Washington, Seattle, WA, 98195, USA

3Department of Electrical and Biomedical Engineering, University of Nevada, Reno, NV, 89557-0260,USA

4Department of Physics, Tbilisi State University, I. Chavchavadze av., 1, Tbilisi, 0128, Georgia

Corresponding author: N. Tugushi (e-mail: tugushinika96@gmail.com).

ABSTRACT Using WKB method the peculiarities of the temporal spectrum of an ordinary and

extraordinary electromagnetic wave scattered in a weakly randomly inhomogeneous three-dimensional

nonstationary and conductive magnetized plasma are investigated. On the basis of the stochastic differential

transport equation for the frequency fluctuation the broadening and the displacement of the temporal

spectrum for both waves are obtainedfor the polar terrestrial ionosphere. These statistical characteristics

contain anisotropic parameters: velocity of a plasma stream, conductivitiesof the ionosphere, elongated

electron density irregularities are characterized by the anisotropy factor and inclination angle with respect

to the geomagnetic lines of forces. The analysis of the power spectrum of the waves as a function of the

propagation distance and the nondimensional frequency parameter containing the carrier frequency and

characteristic temporal scale of electron density fluctuations are carried out. Analytical and numerical

calculations have shown that the terrestrial conductivity and anisotropy factors exert a substantial influence

on evaluationof the temporal spectrum than the inclination angle. It was foundthat the wave spectrum

increases initially as the square root of the propagation distance, but at large distances it approaches a

limiting value. Statistical moments of a scattered ordinary and extraordinary waves do not depend on an

absorption sign and valid for both absorptive and active media.

INDEX TERMS Statistical moments, temporal spectrum, turbulent magnetized plasma.

I.

INTRODUCTION

S is well-known, turbulent media are characterized by

macroscopic motion, chaotical nonstationarity and

inhomogeneity. Statistical characteristics of wavesin

random media withrandomly varying spatial irregularities

are studied well [1-4] but immediateaction of the

movement of the environment and its nonstationarity on the

statistical characteristics of scattered waves is not studied in

detail. Nonstationarity may be substantial and cause

changes of properties of the considered waves. Meanwhile,

the effect of accumulation of fluctuations of wave

parameters is revealed more brightly at big distances from a

source at existence of regular absorption in the non-

stationary medium [5].

The problem is of importance since the performance of

various existing and developing communication systems

depend on the statistical properties of the signals after

propagating through the transmission medium. In most

cases using results derived applying geometrical optics and

the parabolic approximation. This imposes any restrictions

on the distance travelling by wave in random medium.

Broadening and shift of maximum of the spatial power

spectrum of scattered electromagnetic waves in the

geometrical optics approximation were considered in [6-9].

Evaluation of the temporal spectrum of an incident

narrow band wave field in a nonstationary medium is

characterized by both amplitude and frequency modulation.

Transport theory to study frequency spectra of beam waves

propagating in a turbulent atmosphere was used in [10].

Spectral broadening has also been considered in [11]. Their

investigation was based on the parabolic approximation

with “frozen” turbulence model [12]. The behavior of the

temporal (frequency) spectrum of multiple scattered

electromagnetic waves in the collisionless turbulent non-

magnetized plasma has been investigated in [13,14]. Non-

stationarity is caused due to plasma motion. It was shown

that power spectrum of wave has the Gaussian shape with

the displaced maximum. Width of the spectrum coincides

with variance of the frequency fluctuation calculated in the

geometrical optics approximation by the perturbation

method.

In many papers the fluctuating medium is considered as

nonabsorptive. The influence of absorption (conductivity of

A

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Conference Paper

Jan 2024

... Generally, the propagation of a wave with a complex spectral structure continuously changes its spectrum. The features of the temporal spectrum in the polar ionosphere have been considered in the study by Jandieri et al. [11] . ...

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