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Volume 60, Nº 5 (2017)

Article

Refraction of Radio Waves on the Radio-Occultation Satellite-to-Satellite Paths as a Characteristic of the Atmospheric State

Matyugov S., Yakovlev O., Pavelyev A., Pavelyev A., Anufriev V.

Resumo

We present the results of analyzing the radio-wave refractive characteristics measured on the radio-occultation paths between the GPS navigation satellites and the FORMOSAT-3 research satellites in the central region of the European territory of Russia in 2007–2013. The diurnal, seasonal, and annual variations in the refraction angle at altitudes of 2 to 25 km are discussed. It is shown that the refraction angle can be used as an independent characteristic of the atmospheric state and its long-term variation trends. Diurnal and nocturnal variations in the refraction angle in the winter and summer seasons are analyzed. Trends in the atmospheric refraction variations over seven years are discussed.

Radiophysics and Quantum Electronics. 2017;60(5):347-354
pages 347-354 views

Impact of a Strong Magnetic Storm and Two X-Ray Flares on the Ionospheric HF Channel in the Summer Solstice of 2015 According to Oblique Sounding in the Eurasian Region

Uryadov V., Kolchev A., Vertogradov G., Vybornov F., Egoshin I., Sklyarevsky M., Shumaev V., Chernov A.

Resumo

We present the results of observations of the impact a strong magnetic storm and two X-ray flares in the summer solstice of 2015 on the HF signal characteristics during oblique sounding of the ionosphere in the Eurasian region. It was found that the negative phase of the magnetic storm led to a strong degradation of the ionospheric channel, up to a long blackout on the paths adjacent to the subauroral latitudes. On the midlatitude paths, a decrease in the maximum observable frequency of the F layer reached 50% with respect to the average values for an undisturbed ionosphere. The propagation velocity of the negative phase of a disturbance from the subauroral to the midlatitude ionosphere is determined (it is equal to about 100 m/s). It is shown that during a magnetic storm the least observable frequency and the average signal-to-noise ratio for the propagation mode via the sporadic Es layer correlate well with the auroral AE index. Anomalous signals were detected in the main phase of the magnetic storm on the Cyprus—Rostov-on-Don path when a chirp ionosonde–radio direction finder was operated in the over-the-horizon HF radar mode. On the basis of modeling and comparison with experimental data, it is shown that the anomalous signals are due to scattering of radio waves by small-scale irregularities located in the subauroral ionospheric F region.

Radiophysics and Quantum Electronics. 2017;60(5):355-373
pages 355-373 views

Lightning-Discharge Initiation as a Noise-Induced Kinetic Transition

Iudin D.

Resumo

The electric fields observed in thunderclouds have the peak values one order of magnitude smaller than the electric strength of air. This fact renders the issue of the lightning-discharge initiation one of the most intriguing problems of thunderstorm electricity. In this work, the lightning initiation in a thundercloud is considered as a noise-induced kinetic transition. The stochastic electric field of the charged hydrometeors is the noise source. The considered kinetic transition has some features which distinguish it from other lightning-initiation mechanisms. First, the dynamic realization of this transition, which is due to interaction of the electron and ion components, is extended for a time significantly exceeding the spark-discharge development time. In this case, the fast attachment of electrons generated by supercritical bursts of the electric field of hydrometeors is balanced during long-term time intervals by the electron-release processes when the negative ions are destroyed. Second, an important role in the transition kinetics is played by the stochastic drift of electrons and ions caused by the small-scale fluctuations of the field of charged hydrometeors. From the formal mathematical viewpoint, this stochastic drift is indistinguishable from the scalar-impurity advection in a turbulent flow. In this work, it is shown that the efficiency of “advective mixing” is several orders of magnitude greater than that of the ordinary diffusion. Third, the considered transition leads to a sharp increase in the conductivity in the exponentially rare compact regions of space against the background of the vanishingly small variations in the average conductivity of the medium. In turn, the spots with increased conductivity are polarized in the mean field followed by the streamer initiation and discharge contraction.

Radiophysics and Quantum Electronics. 2017;60(5):374-394
pages 374-394 views

Nonadiabatic Electron-Optical System of a Technological Gyrotron

Goldenberg A., Glyavin M., Leshcheva K., Manuilov V.

Resumo

We consider a new version of the nonadiabatic system for the formation of a helical electron beam in a gyrotron, in which electrons acquire initial oscillatory velocities when a rectilinear beam is injected at an angle to the magnetic field. In such an electron gun, the influence of thermal electron velocities and roughness of the emitting surface can be decreased, as compared with the conventional electron-optical systems of gyrotrons. This makes it possible to increase significantly the system efficiency. The main factors affecting the quality of the formed beam are considered.

Radiophysics and Quantum Electronics. 2017;60(5):395-400
pages 395-400 views

The Diamond Window with Boron-Doped Layers for the Output of Microwave Radiation at High Peak and Average Power Levels

Ivanov O., Kuzikov S., Vikharev A., Vikharev A., Lobaev M.

Resumo

We propose a novel design of the barrier window for the output of microwave radiation at high peak and average power levels. A window based on a plate of polycrystalline CVD diamond with thin (nanometer-thick) boron-doped layers with increased conductivity is considered. Such a window, which retains the low radiation loss due to the small total thickness of the conductive layers and the high thermal conductivity inherent in diamond, prevents accumulation of a static charge on its surface, on the one hand, and allows one to produce a static electric field on the surface of the doped layer, which impedes the development of a multipactor discharge, on the other hand. In this case, a high level of the power of the transmitted radiation and a large passband width are ensured by choosing the configuration of the field in the form of a traveling wave inside the window.

Radiophysics and Quantum Electronics. 2017;60(5):401-408
pages 401-408 views

Determination of the Boundary Transition Temperatures in Polypropylene on the Basis of Measurements in the Terahertz Band

Kitai M., Nazarov M., Nedorezova P., Shkurinov A.

Resumo

We propose a method for determination of the boundary temperatures of transitions in the structure of polymers by means of analyzing the refractive index of these materials in the terahertz band. The temperatures of glass transition, crystallization, and melting are determined experimentally for isotactic and syndiotactic polypropylenes. Such polymers have low absorption coefficients in the terahertz band. The behavior of intermolecular oscillations of the macromolecules, which are active in polymer spectra in this frequency band, is analyzed.

Radiophysics and Quantum Electronics. 2017;60(5):409-416
pages 409-416 views

The Time Dependence of a Quasimonochromatic Signal in the Region of Destructive Two-Beam Interference

Bukhman N.

Resumo

We consider the time dependence of a total signal from two point acoustic sources emitting similar quasimonochromatic signals (two-beam interference of quasimonochromatic waves). It is shown that the time dependence of the envelope function of the total signal is close to the time dependence of the envelope function of the signal from one source with accuracy up to the delay time. The delay time varies within the limits from the usual (geometric) time in the light bands of the interference field (the constructive-interference region) to the zero one (within the framework of the considered approximations) in the dark bands (the destructive-interference region). At the intermediate points of the interference field, the delay time appears to be complex, i.e., the signal is not only shifted in time, but also distorted.

Radiophysics and Quantum Electronics. 2017;60(5):417-429
pages 417-429 views