On the reflection of a radiowave beam from a plasma layer with large-scale inhomogeneities

Using the method of parabolic equation (MPE), we obtain transfer equations for the mean field, the space-coherence function, and the ray intensity of a radiowave beam as it is reflected from a plasma layer with random inhomogeneities. The general solutions of these equations are found. Special attention is given to the case of radiowave beam reflection from a linear plasma layer with large-scale electron-density inhomogeneities. If a weakly directed transceiving SW antenna is used, the shortwave scattering can lead to a pronounced (of the order of 3 dB) decrease in the intensity of a vertical-sounding signal reflected from the ionospheric F2 layer only under the conditions of abnormally strong ionospheric electron-density perturbations. Radiophysical Research Institute, Nizhny Novgorod, Russia. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Radiofizika, Vol. 41, No. 8, pp. 955–965, August, 1998.     

Evolution of wave perturbations in the upper ionosphere

We analyze the propagation of wave perturbations of plasma density in the outermost part of the ionospheric F-region. It is shown that growing oscillations can propagate downwards along the geomagnetic field lines. Such perturbations can form random inhomogeneities in the upper ionosphere. State University, Irkutsk, Russia. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Radiofizika, Vol. 41, No. 4, pp. 432–437, April, 1998.     

Acoustic-gravity waves in the Earth’s atmosphere generated by surface sources

The generation of acoustic-gravity waves and their propagation in the Earth’s atmosphere is analyzed numerically on the basis of a computer model of the stratified atmosphere with dissipation. Atmospheric and ionospheric wavelike disturbances from different surface sources such as earthquakes, explosions, seiches, temperature heating, and tsunamis are studied.     

New Results of Studying the Lower Ionosphere by the Method of Resonance Scattering of Radio Waves from Artificial Periodic Inhomogeneities

We present the results of studying the lower ionosphere in 2000–2004 at the “Sura” heating facility by the method of resonance scattering of radio waves from artificial periodic inhomogeneities of the ionospheric plasma. Experimental data on a study of the sunset–sunrise phenomena in the ionospheric D region and the possibility of determining the concentrations of atomic oxygen and excited molecular oxygen are discussed. The results of studying the sporadic layers of ionization are presented and the method for a study of ion composition of the E_s layer is discussed. Data of the August 2004 experiments on a study of the influence of heating the ionosphere on the E_s layer and characteristics of artificial periodic inhomogeneities are presented. Prospects for further research are discussed. __________ Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Radiofizika, Vol. 48, No. 9, pp. 757–771, September 2005.     

Electric fields of ionospheric plasma at low latitudes

A mathematical—physical model is proposed for the electric fields and currents of ionospheric plasma, which is capable of describing the altitude variations of these electrodynamic parameters. The results obtained by solving of the model problem are analyzed. It is shown that the distribution of the electric fields and currents of ionospheric plasma has significant inhomogeneities that must be taken into account in solving problems related to the electrodynamics of ionospheric plasma.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 4, pp. 41–47, April, 1996.     

On fractal structure of large-scale electron-density inhomogeneities of traveling disturbances in the midlatitude ionosphere

We present the results of studies of the multifractal structure of slow (of duration τ ≈ 10 s) fluctuations of the received-signal amplitudes in special experiments on radio-raying of the midlatitude ionosphere by signals from orbital satellites in 2004–2006. It is shown, in particular, that the method of multifractal analysis of amplitude records of the received signals yields information on the spectrum of large-scale ionospheric inhomogeneities, which is inaccessible for the classical method of radio scintillations. From the results of measurements with the use of multifractal processing of experimental data, we found that large-scale (tens of kilometers) quasiregular electron-density inhomogeneities of traveling ionospheric disturbances (TIDs) have a power-law spectrum. It is exactly the power-law form of the spatial spectrum of large-scale inhomogeneities of TIDs that can be the reason for the observed multifractal structure of the intermittency of slow fluctuations of the received-signal amplitudes. However, under conditions of a developed small-scale turbulence of TIDs, the observed multifractal structure of the received signals is, as a rule, stipulated by the spatial inhomogeneity of the variance of the integral electron-density fluctuations of small-scale inhomogeneities on scales comparable with the sizes of large-scale inhomogeneities of TIDs. __________ Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Radiofizika, Vol. 51, No. 3, pp. 191–198, March 2008.     

Variations of mode amplitudes in a range-dependent waveguide

The ray method of calculating the mode amplitudes is used to analyze the sound fields in deep-water acoustic waveguides with two types of inhomogeneities of the refractive index: (i) weak inhomogeneities that cause small perturbations of ray trajectories and (ii) strong inhomogeneities with large spatial scales. Simple analytical relations are derived for describing the variations of the mode structure of the sound field in the presence of the aforementioned inhomogeneities. A new criterion defining the validity of the adiabatic approximation is formulated. To illustrate and test the results obtained, a numerical simulation of the sound fields is performed on the basis of the parabolic equation method.

     

Some results of synchronous experimental study of artificial F-spread at radiophysical test sites in nizhny novgorod province

We show some results of experiments on synchronous sounding of the ionosphere by short-wave signals at the Radiophysical Research Institute’s test site in Zimenki and Vasil’sursk, Nizhniy Novgorod province, during ionospheric modification by high-power short radiowaves from transmitters of the “Sura” facility in Vasil’sursk. In the course of experiments we proved directly the decisive role of large-scale inhomogeneities of the ionospheric plasma with dimensions of from several kilometers to several dozens of kilometers in the formation of artificial F- spread. The small-scale inhomogeneities with dimensions smaller than 1 km, which are localized in a relatively thin layer near the reflection level of a high-power short radiowave, emerged only at sounding waves, propagating (reflected) in the immediate vicinity of the center of the heating region. Radiophysical Research Institute, Nizhny Novgorod, Russia. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Radiofizika, Vol. 40, No. 6, pp. 688–692, June, 1997.     

Spatially nonlocal model of surface erosion by ion bombardment

A model of solid surface erosion under ion bombardment is proposed. This model takes into account the dependence of the local sputtering yield on the nanoscale relief at a given point and the point of incidence of a primary ion. Such an approach leads to spatially nonlocal erosion model, which predicts the formation of a wavelike relief in the presence of nanoscale inhomogeneities on the surface.     

Artificial Periodic Inhomogeneities of the Ionosperic Plasma as a Promising Line in the Ionospheric Research

This paper is dedicated to a new method of ionospheric studies, developed at the Radiophysical Research Institute (NIRFI) and based on the creation of artificial periodic inhomogeneities (APIs) of the ionospheric plasma. We review the techniques and present the results of determination of the basic parameters of the ionosphere and atmosphere.     

Vertical Velocities and Temperature of the Neutral Component in the Upper Atmosphere

Results of measurements of the velocity of the vertical plasma motion and the temperature of the neutral component in the upper atmosphere and comparison of variations in these parameters have been described. The measurements have been carried out by the resonance scattering of radio waves by artificial periodic irregularities in the ionospheric plasma. The irregularities arise when the ionosphere is modificated by a powerful high-frequency radio emission from a Sura midlatitude heating facility. Comparison has been conducted using experimental data on altitude- and time-dependent variations in the above parameters obtained in experiments of 2010 and 2014. It has been shown that, above 100 km, wavelike variations in temperature and velocity are commonly observed simultaneously. In the absence of wavelike variations, there is a tendency to an increase in temperature with an increase in the velocity of the vertical plasma motion regardless of direction. This tendency can be attributed to thermal flows directed upward from the turbulent region of the ionosphere.     

Special features of non-one-dimensional thermal diffusion of artificial plasma inhomogeneities during local heating of ionospheric plasma

We study the dynamics of thermodiffusional redistribution of magnetized plasma during local heating of electrons by the field from an HF electromagnetic source. The characteristic regimes of thermodiffusional formation of finite-sized artificial plasma inhomogeneities are analyzed in relation to the Earth’s ionospheric conditions. Results of numerical calculations illustrating features of the dynamics of thermodiffusional redistribution of ionospheric plasma at different altitudes are presented. N. I. Lobachevsky State University, Nizhny Novgorod, Russia. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Radiofizika, Vol. 41, No. 2, pp. 212–221, February, 1998.     

Gyroharmonic properties of the middle-scale artificial ionospheric turbulence during heating of the ionospheric F 2 layer by a high-power O-mode radio wave

We present the results of studying the properties of artificial F-spread that appears on ionograms during heating of the ionospheric F₂ region by a high-power O-mode radio wave. It is shown that the regions of resonant interaction of a high-power radio wave with plasma, where the pump-wave energy is almost totally absorbed and the plasma is subject to intense heating, affect significantly the development of a self-focusing instability of a high-power radio wave and the generation of middle-scale (with characteristic scales across the magnetic field l_⊥ ≈ 0.4–1.5 km) artifical ionospheric inhomogeneities. It is established that the intensity of such inhomogeneities depends on the sign and magnitude of detuning of the pump-wave frequency with respect to the electron gyroresonance harmonic frequency Δf = f_PW − nf_ce and has the minimum value for Δf ≈ −20 kHz, thus demonstrating the asymmetry of the gyroharmonic properties of their excitation mechanism. Relationship between the observed phenomena and known characteristics of the artificial ionospheric turbulence for f_PW ≈ nf_ce is analyzed. __________ Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Radiofizika, Vol. 51, No. 5, pp. 367–375, May 2008.     

Scalar Perturbations in Inflationary Models Based on the Non-Linear Sigma Model

The inflationary models based on the non-linear sigma model with the self-coupling potential are considered. The slow-roll solutions for long-wavelength inhomogeneities in general two-component chiral models and diagonal three-component chiral model of a special case are obtained. Scalar perturbations are calculated for two examples.     

On the spectrum of large-scale inhomogeneities of the upper ionosphere

The possibility of measuring the large-scale turbulence structure of the upper ionosphere by vertical and oblique short-wave (SW) radio-sounding techniques is considered. General expressions have been derived for the phase fluctuation spectrum of a short-wave signal reflected at the ionospheric layer with an arbitrary regular permittivity profile and given spectrum of inhomogeneities. We have analyzed a number of particular cases which are most typical of phase measurements in the vertical and oblique SW radio-sounding of the randomly inhomogeneous ionosphere. It is shown that when these methods are used the phase fluctuation spectra of reflected signals may critically depend on the form of the ionospheric electron density profiles. The correct interpretation of the measurement data requires use of stations of synchronous vertical and oblique sounding to obtain proper ionograms and calculate the current spectra of a regular permittivity distribution of the ionosphere. Specific difficulties in interpreting the phase measurements of ionospheric inhomogeneity spectra by vertical and oblique radio-sounding methods are mentioned.Radiophysical Research Institute, Nizhny Novgorod. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Radiofizika, Vol. 38, No. 7, pp. 653–659, July, 1995.     

Results of studying the sporadic <Emphasis Type="Italic">E</Emphasis> layer by the method of resonant scattering of radio waves by artificial periodic inhomogeneities of the ionospheric plasma

We report on the results of studying the lower ionosphere by a method based on the resonant scattering of radio waves by artificial periodic inhomogeneities of the ionospheric plasma. Different aspects of studying the sporadic E layer such as the influence of the vertical transfer on its formation, the possibility of examination of its ion composition, and the influence of the ionosphere heating on the layer characteristics are discussed. The results of determining the parameters of the E _s layer and some characteristics of the lower ionosphere during the creation of artificial periodic inhomogeneities at two frequencies are presented. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Radiofizika, Vol. 51, No. 11, pp. 956–969, November 2008.     

Studies of the Irregular Structure of the Ionosphere using Scattering of Radio Waves on Artificial Periodic Inhomogeneities

We present new results of our studies of the irregular structure of the ionosphere using artificial periodic inhomogeneities (APIs) of the ionospheric plasma. The observations were carried out from 9:00 to 17:00 in August 10–12, 1999 with a height step of 0.7 km and digital registration and real-time processing of the signal quadratures. It is shown that in many cases, the amplitude of the scattered signal is determined by the interference of radio waves scattered on APIs and on natural ionospheric formations including sporadic layers and large-scale natural irregularities. This allows one to study the irregular structure of the lower ionosphere by analyzing height-time dependences of the amplitude and phase of the scattered signal.     

Spherically symmetric solutions in Macroscopic Gravity

Schwarzschild’s solution to the Einstein Field Equations was one of the first and most important solutions that lead to the understanding and important experimental tests of Einstein’s theory of General Relativity. However, Schwarzschild’s solution is essentially based on an ideal theory of gravitation, where all inhomogeneities are ignored. Therefore, any generalization of the Schwarzschild solution should take into account the effects of small perturbations that may be present in the gravitational field. The theory of Macroscopic Gravity characterizes the effects of the inhomogeneities through a non-perturbative and covariant averaging procedure. With similar assumptions on the geometry and matter content, a solution to the averaged field equations as dictated by Macroscopic Gravity are derived. The resulting solution provides a possible explanation for the flattening of galactic rotation curves, illustrating that Dark Matter is not real but may only be the result of averaging inhomogeneities in a spherically symmetric background.     

Model study of the response of the thermosphere to perturbations of mesospheric tides and planetary waves during a sudden stratospheric warming

The results of numerical simulations of the effects of a sudden stratospheric warming (SSW) in January 2009 are examined. The calculations are performed within the framework of the Global Self-Consistent Model of the Thermosphere, Ionosphere, Protonosphere (GSM TIP), which calculates the parameters of the neutral and charged components of the upper atmosphere. An analysis of the numerical simulation results showed that the perturbation of mesospheric tidal and planetary waves significantly affects the structure of variations of the thermosphere at altitudes below 150 km. At higher altitudes, the characteristics of planetary and tidal waves in the thermosphere are practically insensitive to the corresponding mesospheric perturbations. The calculated space–time structure of ionospheric perturbations caused by mesospheric and planetary tidal waves is in qualitative agreement with observation data. The results show that the main reason for the observed ionospheric effects is the perturbation of the electric fields in the dynamo region. However, the calculated magnitudes of the ionospheric effects produced by the SSW are at least two- to threefold weaker than the observed. It is assumed that, in order to achieve a quantitative agreement between simulation and experimental results on the ionospheric effects of the SSW, it is not enough to consider only the dynamics of planetary and tidal waves in the mesosphere. An additional source of the perturbation of the thermosphere and ionosphere during the SSW may be associated with the propagation of internal gravity waves from the lower atmosphere and their dissipation in the thermosphere.     

Transition radiation of sound under uniform motion of momentum and mass sources in inhomogeneous media

Theoretical investigations of transition radiation of sound under the uniform motion of small momentum and mass (heat) sources in a gas with chaotic inhomogeneities of density and temperature are briefly discussed. We analyze two basic methods for calculating the source losses by the radiation of acoustic waves. The first method is based on the calculation of the energy flux in the Born approximation over small perturbations of the parameters of the medium, and allows us, in particular, to clarify the problem of the angular distribution of the radiation. The second method is based on the use of the effective permittivity tensor, which links together the spatiotemporal Fourier transforms of the average momentum of a unit volume of the medium and the average (over the ensemble) velocity of the wave perturbations. The dependence of the radiation reaction force on the velocity of the motion of source is analyzed for the case of small-scale and large-scale inhomogeneities of the medium.Radiophysical Research Institute, Nizhny Novgorod. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Radiofizika, Vol. 38, Nos. 1–2, pp. 44–55, January–February, 1995.