Showing papers in "Radiophysics and Quantum Electronics in 1994"
TL;DR: In this article, a dynamic model was proposed to explain the relationship between microwave and hard x-ray (hx) emissions in impulsive and prolonged events (variation of intensity ratio, delay of maxima) without assuming additional shock-wave electron acceleration in prolonged bursts.
Abstract: A dynamic model is proposed that explains the relationship between microwave and hard x-ray (hx) emissions in impulsive and prolonged events (variation of intensity ratio, delay of maxima) without assuming additional shock-wave electron acceleration in prolonged bursts. According to this model, energetic electrons enter the burst arch for the entire duration of an hx flare. X-rays are generated chiefly as a thick target is approached, and, therefore, the duration is not a function of the background-plasma density and is determined only by the power of the particle source. On the other hand, microwave generation has a gyrosynchrotron mechanism, and, therefore, its intensity is determined by the instantaneous number of high-energy electrons accumulated in the trap. For the same maximum source power, the maximum number of accumulated electrons at the moment of maximum onset must be directly related to the duration of electron injection and the lifetime of electrons in the trap. The results of this model are confirmed by new empirical regularities: the intensity ratio and delay of the maxima of the microwave and hx flares are increased monotonically with an increase in flare duration, and the nature of these relationships remains unchanged with transition from impulsive to prolonged flares.
35 citations
TL;DR: In this article, the dispersion properties of radio waves with frequencies close to the upper hybrid frequency ωu and the multiple electron cyclotron frequency nωBe (double resonance) are considered for an inhomogeneous plasma with opposite gradients of the electron density and magnetic field magnitude.
Abstract: Dispersion properties of plasma waves with frequencies ω close to the upper hybrid frequency ωu and the multiple electron cyclotron frequency nωBe (double resonance) are considered for an inhomogeneous plasma with opposite gradients of the electron density and magnetic field magnitude. We show that a region of possible solutions of the dispersion relation decreases in real space as well as in wave vector space as of the wave frequency approaches double resonance. The results are applied to an interpretation of experiments on ionospheric modification by high-power radio waves with frequencies close to nωBe.
27 citations
TL;DR: In this paper, the dependences of the properties of diagnostic emission on the parameters of the diagnostic wave, ionospheric conditions, and the level of development of artificial ionosphere turbulence are determined, and criteria are given for selection of optimal diagnostic conditions for ionosphere-plasma sounding.
Abstract: Results of measurements of the characteristics of stimulated electromagnetic emission induced in ionospheric plasma by pulsed high-power radio waves (diagnostic emission) presented. The dependences of the properties of diagnostic emission on the parameters of the diagnostic wave, ionospheric conditions, and the level of development of artificial ionospheric turbulence are determined, and criteria are given for selection of optimal diagnostic conditions for ionospheric-plasma sounding. Results of experiments on the sounding of artificial ionospheric turbulence by means of diagnostic emission are provided. It is established that with transition from daytime to evening conditions, the characteristic times of emission decay are sharply increased. This is attributed to an increase in the natural perturbation of the F-region.
25 citations
TL;DR: In this paper, the results of two experiments with a gyrotron operating at the second gyrofrequency harmonic, using two active electron beams, were reported, and the maximum output power was 0.87 MW at 25% efficiency, beam currents of 57 A and 13 A, and voltage 60 kV.
Abstract: The results of two experiments with a gyrotron operating at the second gyrofrequency harmonic, using two active electron beams, are reported. The internal (additional) beam is coupled weakly to the field by a spurious mode. The currents of the two beams can be controlled independently. The output characteristics of the gyrotons are plotted for various beam currents. The additional beam substantially enhances the operating mode stability and makes an appreciable contribution to the output power. The maximum output power was 0.87 MW at 25% efficiency, beam currents of 57 A and 13 A, and voltage 60 kV. The highest efficiency was 40%. The results suggest that electron-optical systems with two active beams, regardless of some complications of gun design, are promising for short-wave gyrotrons to operate at the fundamental cyclotron resonance. The specific power dissipation in the collector is observed to decrease (in comparison with a single-beam analog).
20 citations
TL;DR: In this paper, the hydrogen peroxide concentrations in water irradiated by electromagnetic energy at frequencies of 2500 MHz and 10000 MHz were measured by means of chemiluminescence, and it was concluded that water dissociation into H and OH groups is a part of the mechanism of microwave-radiation absorption.
Abstract: The hydrogen-peroxide concentrations c(H2O2) in water irradiated by electromagnetic energy at frequencies of 2500 MHz and 10000 MHz are measured by means of chemiluminescence. It is concluded that water dissociation into H and OH groups is a part of the mechanism of microwave-radiation absorption.
16 citations
TL;DR: In this article, the results of a study of the submillimeter rotational spectrum of formamide in states vT=0 and 1 at frequencies of 290-500 GHz were presented.
Abstract: The results of a study of the submillimeter rotational spectrum of formamide in states vT=0 and 1 at frequencies of 290–500 GHz are presented. More than 300 transition frequencies are identified. Watson Hamiltonian constants are obtained for both states.
11 citations
TL;DR: The results of measurements of the growth and decay characteristics of artificial ionospheric radio emission and their dependence on the level of low-frequency artificial turbulence, time of day, and pump-wave frequency are presented in this paper.
Abstract: The results of measurements of the growth and decay characteristics of artificial ionospheric radio emission and their dependence on the level of low-frequency artificial turbulence, time of day, and pump-wave frequency are presented A time delay of the onset of the exponential nature of the decay process is detected, and its characteristics are studied It is shown that the effect is determined by nonlinear pumping over the spectrum of high-frequency plasma turbulence The experimental results demonstrate the possibilities of using artificial radio emission to study the properties of high-frequency plasma turbulence Areas of future research are discussed
11 citations
TL;DR: In this paper, the results of bistatic-radar and transillumination studies of the F-layer under the influence of powerful radio waves (Sura heating facility, Nizhny Novgorod) are presented.
Abstract: The results of bistatic-radar and transillumination studies of the F-layer under the influence of powerful radio waves (Sura heating facility, Nizhny Novgorod) are presented. A highly directional receiving antenna (UTR-2, Kharkov) made it possible to detect and interpret a number of fine-structure characteristics of the Doppler spectrum of a signal scattered by a heated region. It is shown that, in addition to regular drift, there exists relative ordered motion of inhomogeneities in a perturbed region. The relative velocity is estimated. Deformation of the spectrum of a scattered signal in the states of development and relaxation is established and studied, and possible mechanisms of this phenomenon are discussed. Quasi-periodic variations of the amplitude and frequency of a scattered signal with periods of 30 sec to 5 min are detected. A comparison is made with the results of simultaneous radio transillumination of a heated region by signals from the point source Cassiopeia.
9 citations
TL;DR: A basic algorithm is synthesized from which can be derived adjustment algorithms that take into account a priori information on the CM structure that are suitable for adaptive lattice filters.
Abstract: Algorithms for the adjustment of adaptive lattice filters according to a given root of the estimating noise-correlation matrix (CM) are considered. A basic algorithm is synthesized from which can be derived adjustment algorithms that take into account a priori information on the CM structure. Methods for simplification of the algorithm and increasing its efficiency are examined.
9 citations
TL;DR: In this article, the attenuating and refracting properties of wet dust particles with sand and loam nuclei at wavelengths of about 0.1-10 cm were considered and quantitative characteristics of radio-wave attenuation obtained for various models of homogeneous particles with effective permittivity were compared with an exact solution of the electrodynamic problem for two-layer particles.
Abstract: The attenuating and refracting properties of wet dust particles with sand and loam nuclei at wavelengths of about 0.1–10 cm are considered. Quantitative characteristics of radio-wave attenuation obtained for various models of homogeneous particles with effective permittivity are compared with an exact solution of the electrodynamic problem for two-layer particles (“sphere in envelope”). Radio-wave phase variations caused by the presence of dust formations in the medium are determined.
8 citations
TL;DR: Results can be considered evidence that objects with the dimensions of cells are the primary receivers of EHF radiation in the cell culture, and a ratio value d{sub mol}/{lambda} 10{sup -6} is too low to produce space dispersion at the molecular level.
Abstract: It is known that millimeter-wave radiation can cause numerous changes in living organisms. The detection of changes in the states of living organisms is a very complex task, since a complete biological examination is extremely complicated if not practically impossible. As a result, some important aftereffects could be undiscovered. Here we present experimental data on the effects of EHF radiation with left and right circular polarization on a yeast cell culture (Saccharomyces Carlsbergensis). EHF circular polarizers were specially prepared for this. The radiation had a fixed frequency f = 42.19 GHz, power p = 0.12 mW/cm{sup 2}, and 1-hr exposure time. If cell division cycles are synchronized by synchronization of the generated or EHF oscillations under the influence of external coherent EHF radiation, it follows that EHF oscillations chiefly with left circular polarization are excited in the cells. On the other hand, the examined results can be considered evidence that objects with the dimensions of cells are the primary receivers of EHF radiation in the cell culture. A ratio value d{sub mol}/{lambda} {approx} 10{sup -6} is too low to produce space dispersion at the molecular level.
TL;DR: The author examines the physical laws of medicine and biology that determine the maximum possible rate of harmonic regeneration of living organisms and the maximum amount of such regeneration.
Abstract: The author examines the physical laws of medicine and biology that determine the maximum possible rate of harmonic regeneration (ie, a rate that ensures mutually compatible functioning of the various organs and systems) of living organisms and the maximum amount of such regeneration These laws are specific to medicine and biology and are analogs of the first and second laws of thermodynamics
TL;DR: In this paper, the most important statistical characteristics of adaptive antenna arrays are determined, including the mean value and covariance matrix of the vector of the weighting factors, and the powers of the fluctuations of the weights and of the output signal of the array.
Abstract: The most important statistical characteristics of adaptive antenna arrays are determined. These are the mean value and covariance matrix of the vector of the weighting factors, and the powers of the fluctuations of the weighting factors and of the output signal of the array. It is found that under steady-state operating conditions the fluctuations of the vector of the weighting factors lead to a bias of its mean value for an adaptive antenna array without constraints, but the mean value of the weighting vector of an array with constraints and of an array operating using the criterion of the minimum root mean square error is not biased. It is shown that the effect of fluctuations of the weighting vector on the output signal of an adaptive antenna array may be different and is determined by the value of the correlation coefficient between the input-signal read-outs.
TL;DR: In this article, the 1/f noise in thin niobium films manufactured by various technologies and exposed to γ-quantum irradiation and current annealing has been studied.
Abstract: The 1/f noise in thin niobium films manufactured by various technologies and exposed to γ-quantum irradiation and current annealing has been studied. The evaporation conditions (the sublayer material and the substrate temperature) are shown to strongly affect the noise level. Irradiation adds to the film noise, whereas current annealing leads to decrease of the latter. The current dependence of the voltage fluctuations is found to be nonlinear. The fluctuations are proportional to the current in the region of low currents, and they are proportional to the square of the current flowing through the specimen in the region of high currents. The results are interpreted based on the relation of the 1/f noise to the mobile defects of the crystal structure.
TL;DR: A backward wave oscillator (BWO) filled with a strongly magnetized plasma supports TM and Trivelpiece-Gould (TG) modes, and at large amplitudes these modes may act as wigglers for generating millimeter waves via free electron laser instability as discussed by the authors.
Abstract: A backward wave oscillator (BWO) filled with a strongly magnetized plasma supports TM and Trivelpiece-Gould (TG) modes. At large amplitudes these modes may act as wigglers for generating millimeter waves via free electron laser instability. The nonlinear coupling between the wiggler, the beam space charge mode, and the high frequency free electron laser wave is dominated by parallel motions. In the Raman regime the growth rate of instability goes as ∼ ω
pb
1/2
/β
0
9/4
, where ωpb is the beam plasma frequency and β0 is the relativistic gamma factor.
TL;DR: A brief summary of ELF/VLF generation experiments using the SURA heating facility is presented in this paper, where the possibilities of applications of the measured ionosphericaly generated low frequency signal parameters for diagnosing the physical phenomena in the ionosphere and the magnetosphere are discussed.
Abstract: A brief summary of ELF/VLF generation experiments using the SURA heating facility is presented. The possibilities of applications of the measured ionosphericaly generated low frequency signal parameters for diagnosing the physical phenomena in the ionosphere and the magnetosphere are discussed.
TL;DR: In this article, the main equations needed to calculate the efficiency of a gyroklystron in the one-velocity approximation and in the presence of a spread in electron velocities are given.
Abstract: The main equations needed to calculate the efficiency of a gyroklystron in the one-velocity approximation and in the presence of a spread in electron velocities are given. The influence of the longitudinal structure of the static magnetic field on the efficiency of a two-cavity gyroklystron is investigated. The characteristics of a physical model of a gyroklystron for the 3-cm wavelength range are given for different longitudinal magnetic field distributions in the interaction space. The calculated and experimental data are in good agreement.
TL;DR: In this paper, the parameters of free oscillations in gyrotron resonators with a lowered reflection from the diffractive energy output for the purpose of reducing ohmic heating by rf power loss have been calculated.
Abstract: The parameters of free oscillations in gyrotron resonators with a lowered reflection from the diffractive energy output for the purpose of reducing ohmic heating by rf power loss have been calculated. A gyrotron with such a cavity has been studied experimentally. The gyrotron had an efficiency of more than 45% with an output of 350 to 700 kW when operating in the 3.6-mm H11,3 mode.
TL;DR: The results of numerical simulation and experimental study of magnetron injection guns for high-power gyrotrons that form intense helical electron beams are compared in this article, where three types of beams are studied: those with regularly intersecting trajectories, laminar, and mixed trajectories.
Abstract: The results of numerical simulation and experimental study of magnetron injection guns for high-power gyrotrons that form intense helical electron beams are compared. Three types of beams are studied: those with regularly intersecting trajectories, laminar, and mixed (with irregularly intersecting trajectories). The corresponding guns differ in the angle of inclination of the emitting surface to the axis of axial symmetry. Numerical simulation was performed using the EPOS program, which takes into account the effect of the space-charge field on the velocity distribution. The experimental studies of the latter were performed by the retarding-field method. It is established that with allowance for temperature deformations of the electrode systems, the experimental data are in satisfactory agreement with the theoretical. It is shown that for a maximal beam current, the best velocity-distribution characteristics (velocity spread and pitch factor) are provided by guns that form laminar and boundary beams (an intermediate case between laminar and regularly intersecting beams).
TL;DR: In this article, the influence of density ducts on the radiation of given sources in a magnetoplasma was investigated and the authors obtained the full-wave solution for the problem of radiation from annular electric and magnetic currents in the presence of a plasma column (density duct) oriented along an external magnetic field and surrounded by a uniform background magnetic field.
Abstract: We investigate the influence of density ducts on the radiation of given sources in a magnetoplasma. We obtain the full-wave solution for the problem of radiation from annular electric and magnetic currents in the presence of a plasma column (density duct) oriented along an external magnetic field and surrounded by a uniform background magnetoplasma. Both the discrete part of the spatial spectrum of excited waves and the continuous part of the spectrum are considered. We calculate the total radiated power and partial powers radiated in separate eigenmodes guided by the column. It is established that in the whistler frequency range the presence of a channel with enhanced plasma density can cause a considerable increase in the radiation power of annular sources. We give concrete estimations for the ionospheric conditions and compare these results with the results obtained previously for the case of a uniform magnetoplasma without density ducts.
TL;DR: In this article, a method for measurement of distances to nearby thunderstorm discharges in the earth-ionosphere interval is examined that is based on differences in the frequency dependences of the static induction and radiation components of the electromagnetic field.
Abstract: A method for measurement of distances to nearby thunderstorm discharges in the earth-ionosphere interval is examined that is based on differences in the frequency dependences of the static induction and radiation components of the electromagnetic field. Radio-wave reflection from waveguide walls is described by a series of imaginary sources of decreasing amplitude, which allows estimation of the nearzone size, which is about 50 km. It is proposed that the wave impedance of the field be measured to eliminate the effect of the source's spectrum. Simple analytic formulas are obtained that relate characteristic points of the wave-impedance spectrum to the distance to a vertical cloud-earth thunderstorm discharge.
TL;DR: In this article, the results of an investigation of VLF radiation generated by a mobile ionospheric source are presented, which is due to the operation of two powerful HF transmitters at frequencies f and f±F fed to two separate antennas.
Abstract: The results of an investigation of VLF radiation generated by a mobile ionospheric source are presented. Radiation at frequency F appears due to the operation of two powerful HF transmitters at frequencies f and f±F fed to two space-separated antennas. The intensity of the signals received at the ground depends on the location of the source with respect to the receiving point and is determined by the sign and value of the frequency shift F. The proposed model of the phenomena satisfactorily explains the experimental results.
TL;DR: In this article, a rigorous solution of the problem of the excitation of an open stripline resonator by a plane waveguide is obtained on the basis of an approach developed by the authors.
Abstract: A rigorous solution of the problem of the excitation of an open stripline resonator by a plane waveguide is obtained on the basis of an approach developed by the authors. The mechanism of the excitation of an open oscillatory system in a “reflection” configuration is investigated from the viewpoint of electrodynamics for various coupling regimes between the waveguide and the resonator.
TL;DR: In this article, a two-frequency method is proposed for simultaneous determination of the conductivity and dielectric constant of wood in a model of a two component medium to increase the accuracy of moisture-content determination.
Abstract: A two-frequency method is proposed for simultaneous determination of the conductivity and dielectric constant of wood in a model of a two-component medium to increase the accuracy of moisture-content determination.
TL;DR: In this article, the authors studied the diffraction of electromagnetic waves at a corrugated interface between two dielectrics by rigorously solving the integral equation for scattered waves and showed that total anti-specular reflection is possible when the radiation is incident from the denser dielectric.
Abstract: We have studied the diffraction of electromagnetic waves at a corrugated interface between two dielectrics by rigorously solving the integral equation for scattered waves. We show that total anti-specular reflection is possible when the radiation is incident from the denser dielectric, and we find the parameters for a corrugated surface needed to observe this phenomenon.
TL;DR: In this article, the interaction of opposing TE-waves in a nonlinear cubical dielectric located in a waveguide of arbitrary cross-section is examined, and it is shown that the propagation constants of the interacting waves are functions of the combination of the amplitudes of those waves.
Abstract: The interaction of opposing TE-waves in a nonlinear cubical dielectric located in a waveguide of arbitrary cross-section is examined. It is shown that the propagation constants of the interacting waves are functions of the combination of the amplitudes of those waves. Wave reflection and refraction in a nonlinear plate are investigated. A formula for the reflection coefficient and a “trnasillumination” condition of the nonlinear plate are obtained.
TL;DR: It is found that unoccupied regions exist in the vector space of the descriptions of physiologically permissible codes, i.e., there is an excess of code space that could serve for the synthesis of additional channels, including those not inherent in human modalities.
Abstract: The attributes of the afferent flow of the cat analyzer under heat, cold, tactile, and pain stimulation are studied. It is shown the flows formed can be described by an attribute vector. It is found that unoccupied regions exist in the vector space of the descriptions of physiologically permissible codes, i.e., there is an excess of code space that could serve for the synthesis of additional channels, including those not inherent in human modalities. In many problems of engineering and medicine, this could be the only way to restore or compensate for lost functions of analyzing systems, such as vision and hearing.
TL;DR: In this paper, the authors studied a possible connection between the solar microwave precursors and coronal mass ejections (CME) formation and showed that CME initiation is associated with weak soft x-ray emission.
Abstract: There are many results concerning the phenomena of preflare activity and coronal mass ejections (CME) formation. The situation is possible that the CME is the flare response or on the contrary the CME onset initiates the flare. In a number of recent papers R.A. Harrison and his coworkers have shown that CME initiation is associated with weak soft x-ray emission. We have studied a possible connection between the solar microwave precursors and CME. Following this goal, during the period of 1989, 36.5 hour observational samples preceding solar flares were investigated. There were 8 events among them which preceded proton flares. Data have been obtained at four wavelengths (3.2 cm, 10 cm, 30 cm, 46 cm) at the Zimenki Station near Nizhny Novgorod (Russia). To investigate the precursors we used the classification accepted for the description of radio emission bursts in Solar Geophysical Data.
TL;DR: A neural network structure and an algorithm of forming its bond matrix which lead to an approximate but robust solution of the problem are proposed and discussed and various methods of visualizing dynamic processes in a neural network are compared.
Abstract: The problem of developing a neural network with a given pattern of the state sequence is considered. A neural network structure and an algorithm of forming its bond matrix which lead to an approximate but robust solution of the problem are proposed and discussed. Limiting characteristics of the serviceability of the proposed structure are studied. Various methods of visualizing dynamic processes in a neural network are compared. Possible applications of the results obtained for interpretation of neurophysiological data and in neuroinformatics systems are discussed.