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Vol 62, No 6 (2019)

Article

Relationship Between the Polar Electrojet Dynamics and the Amplitude of ELF/VLF Signal from the Ionospheric Source in the Modulated Ionospheric Heating Experiment

Larchenko A.V., Lebed’ O.M., Blagoveshchenskaya N.F., Pilgaev S.V., Beketova E.B., Fedorenko Y.V.

Abstract

We consider the results of the experiment on the polar ionosphere heating by a high-power modulated HF wave conducted by the AARI at the EISCAT/heating facility in October 2016. The data on joint processing of the values of the equivalent polar electrojet current above the heated ionosphere region retrieved by the IMAGE network of ground-based stations and the amplitudes of a signal of the horizontal component of the magnetic field from an ionospheric source at the modulation frequency recorded in the PGI network of high-latitude stations are presented. The events with a strong positive correlation between the magnetic field amplitude variations and the polar electrojet current variations are considered. It is shown that if the direction of the current changes from eastward to northward, correlation between the current variations and magnetic field variations almost disappears at a modulation frequency of 3017 Hz. Temporal and spatial variations of the coefficient of linear regression of the amplitude of the horizontal magnetic-field component with respect to the electrojet current are analyzed. In the transition from day to night, which is accompanied by the electrojet current decrease, the regression slope increases, and it decreases with increasing distance between the heater and the observation point.

Radiophysics and Quantum Electronics. 2019;62(6):385-394
pages 385-394 views

Large-Scale Disturbances in the Lower and Middle Ionosphere Accompanying Its Modification by the Sura Heater

Chernogor L.F., Garmash K.P., Frolov V.L.

Abstract

We briefly describe the results of the first (undedicated) experiments on studying large-scale (about 1000 km) aperiodic and quasi-periodic disturbances in the lower and middle ionosphere. The main results of modern experiments are listed. Multi-instrument radiophysical observations of large-scale (about 1000 km) aperiodic disturbances in the lower ionosphere and quasi-periodic disturbances in the middle ionosphere, which accompanied the Sura heater action with high-power (effective power 40–95 MW) nonstationary radio emission, were performed in 2017–2018 using partial-reflection and vertical/oblique multipath multifrequency sounding techniques. The observations were performed in the observatories of the V. N. Karazin National University of Kharkov during four heating campaigns in 2017–2018. The aperiodic disturbances in the lower ionosphere had a delay time of 15–18 min and a duration of 5–10 min. The disturbances followed the heater switch-on and off. The nature of these disturbances is discussed. The main effects in the middle ionosphere include the following. When the effective radiated power is no less than 40–60 MW, the Doppler spectra become considerably broader and multipathing appears on radio paths that are 1000 km distant from the heater in 40–60 min after the Sura switch-on. Periodic heating of the ionosphere resulted in periodic variations in the Doppler frequency shift (with a maximum deviation of 0.1–0.2 Hz) and in the signal amplitude. The time delay of the ionospheric response lies in the range 40–60 min, while the relative disturbance in the electron density varies from 3% to 12%. Quasi-periodic variations in the Doppler frequency shift and in amplitude are caused by the generation and propagation of waves with 0.2–1.6 km/s speeds and 15–30 min periods. The 0.2–0.4 km/s speeds, as opposed to the 1.6 km/s speed, are regularly observed. The main directions of the future studies of how large-scale aperiodic and quasi-periodic disturbances manifest themselves in the ionosphere and the studies of how these disturbances affect the parameters of radio waves on remote radio paths are also discussed.

Radiophysics and Quantum Electronics. 2019;62(6):395-411
pages 395-411 views

Quasioptimal Projection Method of Doppler Radar Signal Filtering

Fitasov E.S., Orlov I.Y., Nasonov V.V., Bessonova E.V., Kozlov S.A.

Abstract

We propose a method of interperiod signal processing, which is based on the projection Doppler filterting method and used for selection of moving targets. The scheme of using the algorithm of the proposed method for signal processing is presented. The efficiency of this algorithm is assessed with regard to the optimal algorithm of matched filtering for various lengths of signal sampling.

Radiophysics and Quantum Electronics. 2019;62(6):412-419
pages 412-419 views

Analysis of Surface Waves in an Elastic Medium with a Porous Saturated Layer

Lebedev A.V.

Abstract

We study the propagation of seismoacoustic waves in a three-layered medium consisting of a uniform isotropic deformable solid layer that is loaded with a uniform porous layer saturated with fluid. In turn, the porous layer covers a homogeneous isotropic solid half-space. This medium models the geological section in which the upper ground layer is separated from the deep rocks by a porous layer containing a significant amount of fluid. The obtained dispersion relation is analyzed and its solutions for the practically important cases are presented. The effects due to the liquid-phase motion with respect to the relatively deformable solid skeleton during the wave propagation are pointed out. The features of the dispersion curves and the spatial distribution of the mode fields, which allow one not only to determine the presence of a fluid-saturated porous layer under the upper ground layer, but also estimate the thickness and occurrence depth of the porous layer, are revealed.

Radiophysics and Quantum Electronics. 2019;62(6):420-438
pages 420-438 views

Synthetic Crystalline Quartz as an Optical Material for Power Optics

Vlasova K.V., Konovalov A.N., Makarov A.I., Andreev N.F., Kozhevatov I.E., Silin D.E.

Abstract

We present the results of studying Russian synthetic crystalline quartz from the viewpoint of the possibility of its use for manufacturing optical elements of power optics. The results of experimental studies of the absorption and optical nonuniformity of crystal plates with dimensions of 12 × 8 × 1.7 cm as well as theoretical calculations of the thermooptical parameter for the disk configuration of the measured samples, which determines the value of the phase distortions of the wave front of heating radiation, are reported.

Radiophysics and Quantum Electronics. 2019;62(6):439-446
pages 439-446 views