Showing papers in "Radiophysics and Quantum Electronics in 2015"
TL;DR: In this article, the authors studied the interaction of two solitons of different polarities within the framework of the modified Korteweg-de Vries equation, and showed that the third and fourth wave-field moments, which determine the skewness and kurtosis coefficients in the theory of turbulence, decrease, whereas for soliton of different polities, these moments increase.
Abstract: We study interaction of two solitons of different polarities within the framework of the modified Korteweg–de Vries equation. Three types of soliton interaction are considered, namely, exchange and overtaking interactions (for positive solitons) and an absorb-emit interaction (for solitons of different polarities). The soliton-interaction features are studied in detail. Since the soliton interaction is an elementary soliton-turbulence act, the wave-field moments from the first to the fourth inclusively, which are usually considered in the theory of turbulence, are studied. It is shown that during interaction of solitons of the same polarity, the third and fourth wave-field moments, which determine the skewness and kurtosis coefficients in the theory of turbulence, decrease, whereas for solitons of different polarities, these moments increase. The obtained results are compared with the estimates of two-soliton interaction within the framework of the Korteweg–de Vries equation.
25 citations
TL;DR: In this article, the authors evaluate diffraction efficiency and image quality in the process of optical reconstruction of the digital holograms, which are displayed on spatial light modulators (SLM) with 2 and 256 brightness levels.
Abstract: We evaluate diffraction efficiency and image quality in the process of optical reconstruction of the digital holograms, which are displayed on spatial light modulators (SLM) with 2 and 256 brightness levels. The dependences of the above-mentioned parameters on the ratio between the intensities of the object and reference waves during recording of digital holograms are found. Numerically synthesized digital Fresnel holograms were used for modeling of the optical image retrieval. The results of the analysis were used to determine the ratios of intensities of the object and reference waves, at which the best ratios of diffraction efficiency and quality of the optically reconstructed images are achieved in the cases of using the amplitude and phase SLMs.
19 citations
TL;DR: In this paper, the authors proposed a method for calculating the charge distribution along a short cylindrical antenna in an anisotropic medium and the impedance of the antenna, based on the solution of the corresponding integral equation by using a thin antenna approximation for different angles of antenna orientation relative to the anisotropy axes of the medium.
Abstract: We propose a method for calculation of the charge distribution along a short (on the wavelength scale) cylindrical antenna in an anisotropic medium and the impedance of the antenna. The method is based on the solution of the corresponding integral equation by using a “thin” antenna approximation for different angles of antenna orientation relative to the anisotropy axes of the medium. The calculation results coincide with the results obtained earlier by other methods if the antenna axis is not too close to the direction of the asymptote of an open wave-vector surface. The case where the antenna is oriented along this asymptote, in the vicinity of which the angular dependence of the real and imaginary parts of the impedance changes abruptly, is considered in detail.
17 citations
TL;DR: In this paper, the first results of the joint Russian-Ukrainian experiments for recording of signals from the EKB radar of the Institute of Solar-Terrestrial Physics of the Siberian Branch of the Russian Academy of Sciences (Arti observatory, Sverdlovsk region, Russia) at a distance of over 1600 km was presented.
Abstract: We present the first results of the joint Russian–Ukrainian experiments for recording of signals from the EKB radar of the Institute of Solar–Terrestrial Physics of the Siberian Branch of the Russian Academy of Sciences (Arti observatory of the Institute of Geophysics of the Ural Branch of the Russian Academy of Sciences, Sverdlovsk region, Russia) at a distance of over 1600 km by using a coherent receiving system and a high-gain phased array of the UTR-2 radio telescope (S.Ya. Braude Radioastronomical Observatory (RAO) of the Institute of Radio Astronomy of the Ukrainian National Academy of Sciences (IRA UNAS), Kharkov region, Ukraine). It is shown that two pulse sequences that are identical to the transmitted EKB radar signal, but arrive with different delays were observed at the reception point. The sequence which was received first corresponded to the direct-signal propagation along the great-circle arc. The second sequence was received with delays corresponding to a path length of 2800 to 3400 km and was the result of scattering of the transmitted radar signal by high-latitude ionospheric irregularities. The Doppler frequency shift of the scattered signal was range-dependent and varied from −3 to +4 Hz, which corresponded to the radial component of the ionospheric irregularity velocity from −43 to +58 m/s. To interpret the results of the experiments, we numerically simulated the signal propagation based on the actual ionospheric conditions at an appropriate time. Ionospheric characteristics were retrieved by the vertical ionospheric sounding technique, with the ionosonde located in close proximity to the EKB radar. Comparison between monostatic radar diagnostic results and bistatic sounding results has shown a good agreement of the retrieved parameters of the high-latitude ionospheric irregularities.
16 citations
TL;DR: In this article, a method for two-dimensional holographic mapping of the volume of the medium with particles for automatic retrieval of information from the digital particle hologram is discussed, and an algorithm for increasing the quality of the holographic image of a particle is developed.
Abstract: We consider a holographic study of particles. The main attention is focused on retrieval of information from a digital hologram, namely, determination of the characteristics of a particle and its holographic image. To estimate the efficiency of this stage, we used quantitative criteria of the holographic image quality. These criteria were also used for determining the position of a particle in space, which ensures a significantly higher accuracy (an error of about 0.2 mm) compared with other methods. An algorithm for increasing the quality of the holographic image of a particle is developed. A method for two-dimensional holographic mapping of the volume of the medium with particles for automatic retrieval of information from the digital particle hologram is discussed.
14 citations
TL;DR: In this paper, a model of a compact intracloud discharge considered as the result of interaction between two (or more) bipolar streamer structures formed in a strong large-scale electric field of a thundercloud was proposed.
Abstract: We propose a new model of a compact intracloud discharge considered as the result of interaction between two (or more) bipolar streamer structures formed in a strong large-scale electric field of a thundercloud. The model assumes two stages of the compact discharge development. At the preliminary stage, two or more bipolar streamer structures appear successively in the thundercloud in the region of a strong electric field (at the boundaries between the regions of the main positive and the main negative electric charges or between the main positive charge region and the top negative screening layer). The time of development of such structures is determined by the characteristics of the conducting channels that form them and can reach tens of milliseconds. Spatiotemporal synchronization of the bipolar streamer structures is provided by the altitude modulation of the electric field, which, in particular, can originate from a large-scale turbulence of the cloud medium or the stream instability. It is shown that a single bipolar streamer structure accumulates significant electric charges of different signs at its ends as it develops. The start of the main stage of a compact intracloud discharge corresponds to the occurrence of the conducting channel (breakdown of the gap) between the mature streamer structures. The electric charge accumulated at the adjacent ends of the structures at this stage is neutralized over a time much shorter than the duration of the preliminary stage. The parameters of the current pulse are in good agreement with the estimates of the current of a compact intracloud discharge which were obtained in the transmission-line approximation.
13 citations
TL;DR: The issue of small observation samples in the problem of spectral analysis of the random time series is considered and a new algorithm based on the principle of minimum divergence of the cognominal spectral estimates yielded by the results of several independent observations in the Kullback–Leibler information metric is proposed.
Abstract: UDC 537.86+519.2 We consider the issue of small observation samples in the problem of spectral analysis of the random time series. It is proposed to solve the considered problem using the information-theoretic approach and a new algorithm based on the principle of minimum divergence of the cognominal spectral estimates yielded by the results of several independent observations in the Kullback– Leibler information metric. An example of a practical realization of the algorithm is considered and its asymptotic properties are studied. Spectral analysis of the random time series belongs to the most rapidly developing directions in the field of statistical data processing. The problem of small samples has traditionally been a topical issue in this field [1]. This problem has been studied in many works, which stimulated progress in the field of spectral analysis. The nonlinear recurrent methods [2], which are characterized by high resolution under the finite-sample conditions, are in particular referred to the most important recent results. With the advent of them, the problem of choosing the best mathematical tool, i.e., the mathematical model and the method of spectral analysis, with respect to each particular problem has become the most topical in modern studies. In this case, we actually mean choosing the best estimate of the power spectral density within the limits of the finite set {Gj(f )} of the alternatives obtained from the samples xj with the finite sizes nj < ∞ [3]. The above-mentioned problem becomes more urgent if this size decreases. The present work is devoted to the study of this problem in the proposed formulation. In this work, the problem of ill-posed analysis is solved on the basis of the Kullback–Leibler information metric [4] and a new mathematical tool (the principle of minimum information divergence [15] and the whitening-filter method [6]), i.e., it is required to perform mathematical description of the observed process with maximum (in the information-theoretical sense) accuracy using limited ap rioridata. 2. FORMULATION OF THE PROBLEM
13 citations
TL;DR: In this article, a numerical analysis of the laser beam diffraction by a two-zone binary microlens for different focal lengths is presented, and the characteristics and features of diffraction of the Gaussian beam and the (0, 1) Gauss-Laguerre mode with linear and circular polarizations by the considered element are studied.
Abstract: We present a numerical analysis of the laser beam diffraction by a two-zone binary microlens for different focal lengths. Characteristics and features of diffraction of the Gaussian beam and the (0,1) Gauss–Laguerre mode with linear and circular polarizations by the considered element are studied.
13 citations
TL;DR: In this article, the authors describe multitip field emitters with protective coatings, which were developed in Peter the Great St Petersburg Polytechnic University and ensure long-term operation of the emitters under high currents and technical vacuum.
Abstract: We describe multitip field emitters with protective coatings, which were developed in Peter the Great St. Petersburg Polytechnic University. The coatings ensure long-term operation of the emitters under high currents and technical vacuum. Innovative multi-layer emitters composed of contacting nanolayers of materials with different work functions are presented as well. The possibility by using the developed emitters in high-voltage electronic devices is demonstrated.
12 citations
TL;DR: Modified maximum-likelihood algorithms are used to obtain consistent algorithms for estimating the number of radio signals in the case of unknown amplitudes and phases.
Abstract: Some algorithms for estimating the number of radio signals with known and unknown amplitudes and phases are synthesized and analyzed. Modified maximum-likelihood algorithms are used to obtain consistent algorithms for estimating the number of radio signals in the case of unknown amplitudes and phases. Efficiency of the estimation algorithms is quantitatively characterized by the abridged probability of the signal-number estimation error. The studied-algorithm parameters are optimized according to the analysis results.
12 citations
TL;DR: In this paper, the stability of a dense nonequilibrium plasma of the electron cyclotron resonance (ECR) discharge in an open magnetic trap immediately after the end of heating was studied.
Abstract: UDC 533.9.01 We study the stability of a dense nonequilibrium plasma of the electron cyclotron resonance (ECR) discharge in an open magnetic trap immediately after the end of heating. The observed instability is accompanied by pulse-periodic generation of high-power electromagnetic radiation at a frequency that is close to the frequency of the upper hybrid resonance and the double gyrofrequency of electrons and by synchronous precipitations of fast electrons from the trap. It is shown that the observed instability is connected with excitation of plasma waves under the conditions of double plasma resonance in the decaying plasma of the ECR discharge.
TL;DR: In this paper, a complex waveguide resonance diaphragm with an aperture in the form of a rectangular window with two centrally symmetric L-shaped ridges is studied.
Abstract: We solve the problem of electrodynamic analysis of a complex waveguide resonance diaphragm with an aperture in the form of a rectangular window with two centrally symmetric L-shaped ridges. The properties of the diaphragm are studied on the basis of the analysis of the imaginary part of its normalized conductivity. Critical wave numbers and electromagnetic fields are calculated by the partial region technique allowing for the singularity of the electromagnetic field on metal ribs. It is shown that the imaginary part of the normalized conductivity of the diaphragm as a function of the frequency not only turns to zero, but also contains a discontinuity of the second kind, which corresponds to the parallel and series resonance.
TL;DR: In this paper, a model that allows for random time variations in the phase difference Δφ of pairs of waves transmitted through the object is used in the theoretical part of this study.
Abstract: Speckle dynamics in a thin biological object illuminated through a diffusor box is studied both theoretically and experimentally. A model that allows for random time variations in the phase difference Δφ of pairs of waves transmitted through the object is used in the theoretical part of this study. Formulas for the time-averaged intensity of the radiation at a certain point of observation and a temporal autocorrelation function of the radiation intensity are deduced. The relationship between the characteristics of the random variable Δφ and the parameters of the speckle dynamics is discussed. The case of occurrence of a quasiperiodic variation in the radiation intensity is separately considered. The theoretical results are used for interpretation of the data obtained in the experiments on studying the metabolic activity of cells cultivated on a glass substrate.
TL;DR: In this article, a combined optical method for measuring the 3D spectral density of the heights and the time realizations of the surface-wave profiles is proposed, which involves, first, synchronous recording of the optical-brightness field on a rough surface area and the surfaceoscillation measurement at one or several points and, second, filtering of the spatial image spectrum, so that the filter parameters are also chosen from the condition of maximum correlation of the reconstructed and measured surface oscillations at 1 or 2 points.
Abstract: Although optical tools for measuring the surface-wave characteristics provide the best spatial and temporal resolutions compared with other methods, they face some difficulties while converting the results of indirect measurements into the absolute levels of waves. In this paper, we propose a combined optical method for measuring the 3D spectral density of the heights and the time realizations of the surface-wave profiles. The method involves, first, synchronous recording of the optical-brightness field on a rough-surface area and the surface-oscillation measurement at one or several points and, second, filtering of the spatial image spectrum, so that the filter parameters are also chosen from the condition of maximum correlation of the reconstructed and measured surface oscillations at one or two points. The second part of this work deals with the results of measuring the multi-dimensional wave spectra on the basis of the proposed method.
TL;DR: In this paper, the authors measured the wave disturbances of the ionospheric electron number density using the Kharkov incoherent scatter radar and found that the disturbance propagation velocity was near 320-400 m/s and the relative amplitude of the electron density variation was 1-10%.
Abstract: Characteristics of the wave disturbances of the ionospheric electron number density were measured using the Kharkov incoherent scatter radar. The disturbance generation accompanied the SURA heating of the near-Earth plasma by high-power periodic radiation. The distance between the heater and the radar was about 960 km. The possibility of generating ionospheric wave disturbances with a period of 20 to 30 min in the internal gravity wave range was confirmed. The disturbance propagation velocity was near 320–400 m/s, and the relative amplitude of the electron density variation was 1–10%. The wave disturbances appeared in the altitude range 145–235 km. Aperiodic bursts of the electron number density with a relative amplitude of up to 5–10% were detected after the first switch-ons of periodic radiation in the 30-min heating — 30-min pause regime at altitudes of 145 to 310 km. The observation results generally conform to the synchronous observation data obtained using the Kharkov vertical-sounding Doppler radar and a network of ionosondes.
TL;DR: In this paper, the authors studied theoretically the propagation of plane longitudinal acoustic waves in homogeneous media with different-modulus elastic nonlinearity and relaxation, and exact analytical relations were obtained for the profiles of stationary waves and self-similar pulsed and periodic waves propagating in such media with no shape variations.
Abstract: We present the results of studying theoretically of propagation of plane longitudinal acoustic waves in homogeneous media with different-modulus elastic nonlinearity and relaxation. Exact analytical relations are obtained for the profiles of stationary waves and self-similar pulsed and periodic waves propagating in such media with no shape variations.
TL;DR: In this article, the phase liquid-crystal spatial light modulator HoloEyePLUTOVIS was used as an encoding element in the image optical encryption scheme with spatially incoherent illumination.
Abstract: We describe application of the phase liquid-crystal spatial light modulator HoloEyePLUTOVIS as an encoding element in the image optical encryption scheme with spatially incoherent illumination. Optical encryption and numerical decryption of test images were conducted. The results of experiments demonstrate the efficiency of the constructed optical encryption scheme.
TL;DR: In this article, the authors present the results of measuring three-dimensional spectra of the water-surface height distributions in the closed sea and lake-water areas with low-level waves.
Abstract: UDC 551.466.3+551.46.086+004.932 In the second part of the work, which is dedicated to the methods of studying the wave characteristics, we present the results of measuring three-dimensional spectra of the water-surface height distributions in the closed sea- and lake-water areas with low-level waves. The data on the wave spectra is obtained on the basis of processing the wave video images using the energy and correlation approaches. On the whole, the obtained information on the multidimensional characteristics of the waves agrees with the theoretical concepts and the results of other studies.
TL;DR: In this article, the results of the first simultaneous ground-based microwave measurements of the middle-atmosphere ozone and temperature performed at the beginning of 2012 above Nizhny Novgorod (56 N, 44 E) during a sudden stratospheric warming are presented.
Abstract: We present the results of the first simultaneous ground-based microwave measurements of the middle-atmosphere ozone and temperature performed at the beginning of 2012 above Nizhny Novgorod (56 N, 44 E) during a sudden stratospheric warming. The detected features of the atmosphere dynamics are compared with satellite sounding data from an MLS instrument onboard the Aura satellite.
TL;DR: In this paper, the authors estimate the additional absorption of millimeter and submillimeter wavelengths in water vapor arising from collisional interaction of molecules due to the induced dipole moment.
Abstract: This work is devoted to estimation of the additional absorption of millimeter and submillimeter wavelengths in water vapor arising from collisional interaction of molecules due to the induced dipole moment. Absorption is modeled on the basis of ab initio data on the magnitude of the water molecule dipole moment at high densities, and common knowledge of the water vapor absorption spectrum. Using the model developed, we obtained a simple analytical expression for the absorption coefficient as a function of temperature, pressure, and frequency. Comparison of the results with known experimental data leads to the conclusion that in the range of pressures and temperatures typical of water vapor in the Earth’s atmosphere this type of absorption is negligible compared with the absorption arising due to association or dimerization of the water vapor molecules.
TL;DR: In this article, the results of analysis of the ionospheric airglow in the red and green lines of atomic oxygen on the pump-wave frequency f76561 0 near the fourth electron gyroharmonic 4f fixme ce were presented.
Abstract: We present the results of analysis of the dependence of the ionospheric airglow in the red (630 nm) and green (557.7 nm) lines of atomic oxygen on the pump-wave frequency f
0 near the fourth electron gyroharmonic 4f
ce. The experimental data were obtained in 2012 using the SURA heating facility. Stimulated electromagnetic emission spectra were used to determine the relation between f
0 and 4f
ce. It is found that at f
0 > 4f
ce and δf = f
0 − 4f
ce ≈ 15–20 kHz the red-line airglow intensity is about a factor of 1.5 higher for the magnetic zenith pumping (when the pump beam is inclined 12° south of the magnetic field direction) than for the vertical pumping. In the green line for the same offsets δf, the airglow was recorded with confidence only during magnetic zenith pumping. During vertical pumping, no regular dependence of the red-line airglow intensity on δf in the range −15 < δf < 280 kHz was obtained, while the green-line airglow was observed at 15 < δf < +5 kHz and 230 < δf < 280 kHz. In the red line during vertical pumping, a change from the artificial airglow generation to the ionospheric background suppression was detected when the F-layer cutoff frequency was decreased. During magnetic zenith pumping, a wide (about 30°) background suppression zone was observed around the airglow spot with an about 6° angular width.
TL;DR: In this article, the results of experimental and theoretical studies of generation of terahertz radiation during reflection of a femtosecond-long laser pulse from a metal surface were presented.
Abstract: We present the results of experimental and theoretical studies of generation of terahertz radiation during reflection of a femtosecond-long laser pulse from a metal surface. It is shown that a greater part of the experimental results (narrow directivity of the terahertz waves and dependence of its energy on the polarization and incidence angle of the laser radiation) can be interpreted within the model of Cerenkov radiation. Some new features of generation of terahertz radiation are considered, which appear during an optical breakdown of the medium near the metal surface. Structural changes in the terahertz signal, which take place in the process of formation of the near-surface plasma, are studied.
TL;DR: In this article, a maximum-likelihood algorithm for detecting a radio signal with an arbitrary envelope shape, which is observed against the background of additive Gaussian white noise, is presented.
Abstract: We develop the maximum-likelihood algorithm for detecting a radio signal with an arbitrary envelope shape, which is observed against the background of additive Gaussian white noise. The signal duration, amplitude, and initial phase are unknown. The developed algorithm is analyzed on the assumption of sufficiently large signal-to-noise ratios. Asymptotic expressions for the detection-error probabilities are obtained. The developed-algorithm efficiency is checked by computer simulation and the applicability range of the obtained asymptotic expressions for the algorithm characteristics is determined.
TL;DR: In this article, the spectral and holographic characteristics of a novel material designed for manufacture of photothermorefractive (PTR) glass are compared. And the amplitude of modulation of the first harmonic in the refraction factor for the modified PTR glass is twice as high as that within the classical approach.
Abstract: We compare spectral and holographic characteristics of a novel material designed for manufacture of photothermorefractive (PTR) glass. The parameters of holograms recorded in classical and modified PTR glass are confronted. It is shown that unlike the classical PTR glass, the modified PTR glass does not have an additional absorption band in the blue-green spectral region. This allows one to record purely phase holograms in the visible spectral range. The amplitude of modulation of the first harmonic in the refraction factor for the modified photothermorefractive glass is twice as high as that within the classical approach.
TL;DR: In this article, a model of the intracloud lightning discharge formation is presented, where the lightning formation is described as a stochastic growth of the branching discharge channels, which is determined by the electrostatic field.
Abstract: This paper aims at analyzing the broadband part of electromagnetic emission from thunderclouds in a frequency range of tens of kilohertz to hundreds of megahertz. A model of the intracloud lightning discharge formation is presented. The lightning formation is described as a stochastic growth of the branching discharge channels, which is determined by the electrostatic field. The dynamics of the electric field and of the charge distribution over the lightning structure is calculated deterministically. The effect of the initial charge density in the cloud and the parameters of the conducting channels on spatio-temporal characteristics of the currents and structure of the lightning discharge is studied. The discharge radio emission is calculated by summing up the radiation fields of each channel at the observation point. The standard model for a separate discharge current is adopted, and the electromagnetic radiation in the far zone is estimated. It is found that the obtained frequency spectra exhibit a universal power-law behavior. The results of the modeling agree with known experimental data.
TL;DR: In this article, the basic sizes characterizing the morphology of a few practically important synthetic organic polymers in the glassy and viscoelastic states are confronted with the maxima of the absorption spectra in the terahertz frequency range.
Abstract: The basic sizes characterizing the morphology of a few practically important synthetic organic polymers in the glassy and viscoelastic states are confronted with the maxima of the absorption spectra in the terahertz frequency range. These sizes are determined using the X-ray diffraction technique. The absorption spectra of these polymers have been measured by the method of terahertz time-domain spectroscopy in the temperature range from helium to room temperatures.
TL;DR: The dynamics of speckles in the image plane of a monolayer of cells cultivated on a glass substrate has been recorded in this article, where three cell cultures, HEL-3, L-41, and Vero, were selected as the objects of research.
Abstract: The dynamics of speckles in the image plane of a monolayer of cells cultivated on a glass substrate has been recorded. Cell cultures HEL-3, L-41, and Vero were selected as the objects of research. The digitized value of the radiation intensity I in one pixel and the parameter η characterizing the change in the intensity distribution on an 10 × 10 pixel area was recorded for 24 hours. The multiple determinacy coefficient of three cell cultures, which was obtained from the time dependences of η, was equal to 0.94.
TL;DR: In this paper, the authors studied the electrodynamic characteristics of an antenna having the form of an infinitesimally thin, perfectly conducting narrow strip located on a plane interface of a resonant magnetoplasma and an isotropic medium.
Abstract: We study the electrodynamic characteristics of an antenna having the form of an infinitesimally thin, perfectly conducting narrow strip located on a plane interface of a resonant magnetoplasma and an isotropic medium The antenna is perpendicular to an external magnetic field and is excited by a given voltage Singular integral equations for the antenna current, on the basis of which the current distribution is found in the case of an infinitely long radiator, are obtained The limits of applicability of an approximate method based on the transmission line theory for determining the current distribution and input impedance of the antenna are established Within the framework of this method, the results obtained are generalized to the case of a finite-length strip antenna
TL;DR: In this article, the authors studied the electromagnetic wave propagation near the electron cyclotron resonance region in axisymmetric magnetic traps and obtained the ray paths with allowance for the plasma density inhomogeneities, magnetic field direction, and magnetic field strength.
Abstract: Some features of the electromagnetic wave propagation near the electron cyclotron resonance region in axisymmetric magnetic traps are studied both analytically and numerically. The ray paths are obtained with allowance for the plasma density inhomogeneities, magnetic field direction, and magnetic field strength. Criteria for the limiting cases of constructive refraction (the ray paths are attracted to the trap axis, where effective absorption takes place) and destructive refraction (the ray paths are expelled from the trap axis, and efficient heating of the central part of the plasma column is not possible) are found. It is shown that the inhomogeneities of the magnetic field direction and plasma density, which are typical of axisymmetric magnetic traps, as well as the spatial dispersion effects, can strongly affect the electromagnetic wave propagation near the electron cyclotron resonance surface.
TL;DR: The results of the radio-occultation experiments which were carried out for six years in two equatorial regions of the lower ionosphere were analyzed in this paper, where the features of the decimeter radio-wave amplitude variations were considered for the case of remote sensing of the different sporadic structures along the radio paths between two satellites.
Abstract: We analyze the results of the radio-occultation experiments which were carried out for six years in two equatorial regions of the lower ionosphere. The features of the decimeter radio-wave amplitude variations are considered for the case of remote sensing of the different sporadic structures along the radio paths between two satellites. The diurnal dependences of the height and thickness of the Es layer are presented for different time intervals. It is shown that in different days in the nighttime the Es-layer plasma structures can exist in the form of a single layer or in the form of two layers simultaneously. The first layer is located at an average altitude of 116 km, while the second one, at 96 km. It was found that in the daytime the height of the first layer decreases, while in the evening, irregular structures are formed at altitudes distributed randomly between 90 and 100 km. The amplitude variations of the sounding signals are discussed for cases where the distance (in the perigee) of the radio ray path from the Earth’s surface is between 70 and 85 km in the mesosphere. Statistics of the sporadic structure occurrence is given for the regions located in Africa and Indonesia.