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Том 61, № 5 (2018)
- Год: 2018
- Статей: 7
- URL: https://journal-vniispk.ru/0033-8443/issue/view/15171
Article
Characteristics of the Plasma Disturbance Excited at Altitudes of 450–500 km During the “Sura” Facility Operation
Аннотация
We discuss the results of measuring characteristics of the artificial plasma disturbances excited at altitudes of 450–500 km with the ionospheric F2 layer modified by high-power HF radio waves from the Sura facility. It is found that at these altitudes there are plasma temperature and density variations in the HF-perturbed magnetic flux tube. No ducts with increased plasma density that were previously observed at altitudes of about 660 km were detected. The results of the studies are compared with the data from the DEMETER satellite and the results of radiotomographic measurements. It is noted that the field-aligned currents induced in a perturbed ionosphere during the Sura operation were detected for the first time using SWARM satellites.
319-331
Estimation of Broadening of the Spectra of Short Surface Waves in the Presence of Long Waves
Аннотация
We perform a numerical simulation of evolution of the wind waves, which is based on solving the Euler equations for a two-dimensional potential flow and, therefore, allows for the nonlinear effects. Analysis of the obtained realizations of the surface profiles shows that the proposed direct numerical simulation allows one to reproduce the features of modulation of short surface waves. The model dependence, which describes the characteristic deviation of the spectral density from the dispersion curve on the frequency–wave number plane, is obtained. Comparison with the wave spectra measured under natural conditions is indicative of a qualitative agreement between the calculated and experimental results.
332-341
Relativistic Backward-Wave Oscillator with Parallel Wave Interaction
Аннотация
We study operation of a backward-wave oscillator (BWO) in the regime of parallel amplification of rotating waves with different azimuth indices. It is shown that in the linear case, the use of the parallel wave interaction principle allows one to enhance the BWO gain significantly as compared with a classical backward-wave oscillator. An option for using parallel amplification in high-power sectioned amplifiers is proposed.
342-349
Application of the Method of Moments for Calculating Electrodynamic Characteristics of a Quasistatic Antenna in an Anisotropic Medium
Аннотация
We develop the numerical method of moments for solving an integral equation that describes the distribution of the charge along a thin finite-length antenna wire in an anisotropic medium in the quasistatic approximation. It is shown that the method of moments can be used to calculate the electrodynamic characteristics of such an antenna under the conditions where the kernel of the integral equation has a singularity related to the resonance cone. The influence of the ratio between the elements of the dielectric permittivity tensor and the method of partitioning of the antenna surface on the calculation accuracy is analyzed. It is shown that the relative error of calculations of the antenna characteristics is a fairly small value of about 1% if the antenna wire is divided into ten segments.
350-361
Electrodynamic Analysis of a Circular Waveguide with Thin Metal Ribs
Аннотация
We solve the problem of electrodynamic analysis of the mode composition of radiation in a circular waveguide with thin radial metal ribs. Algorithms for calculation of cutoff wave numbers and components of the electromagnetic fields of the H and E modes have been developed with allowance for the singularity of the field behavior near a thin metal rib. Spectral characteristics of the waveguide are studied. Structures of the electromagnetic fields of the fundamental mode and the higher modes are determined.
362-373
On the Fractal Absorption Spectra of Polymers in the Low-Frequency Part of the Terahertz Range
Аннотация
The power dependence α(ν) ∝ νμ, where μ > 0 is the power exponent which is noninteger in the general case, is observed for amorphous polymers with a small absorption coefficient α in the low-frequency part of the terahertz range, which approximately corresponds to the frequencies ν from 0.1 to 2–3 THz. This dependence is fractal, which is due to the fractal structure of the polymer macromolecules. In this work, we find the power-law index at room temperature for the absorption coefficient of some amorphous polymers. This index is determined on the basis of the dynamics of transmission of a broadband picosecond terahertz pulse through the polymer sample, i.e., using the method of the pulse terahertz spectroscopy in the time-domain representation.
374-381
Measurement of the Brightness Temperature of the Fast Gas-Dynamics Processes using the EHF Radiointerferometer Radiometer in the Presence of Active-Channel Signal
Аннотация
We show the results of simultaneous measurements of the brightness temperature and the detonation-front motion in a trinitrotoluene sample. The measurements were performed using the EHF radiointerferometer radiometer developed at Yu. E. Sedakov Research Institute of Measurement Systems. The algorithms and the methods for the recorded-signal processing are described.
382-388