M.S. Sklyarevsky – Master, Post-graduate Student, 

JSC «VNII «Gradient» (Rostov-on-Don)

E-mail: mssklyarevsky@gmail.com

G.G. Vertogradov – Dr.Sc.(Phys.-Math.), Professor, 

Southern Federal University (Rostov-on-Don); JSC «VNII «Gradient» (Rostov-on-Don) E-mail: vertogradovgg@gmail.com

In this paper the method of investigation of traveling ionospheric disturbances by means of LFM ionosonde-direction finder is proposed. The distinctive feature of the developed approach is the simultaneous measurement of entire set of frequency characteristics of the ionospheric channel at controlled propagation path. It includes range-frequency (RFC), amplitude-frequency (AFC) and twodimensional angular-frequency characteristics. At this paper the mathematical description and operational algorithm of the LFM ionosonde-direction finder are presented.

The developed method was applied to the results processing of the experiment carried out from January 2013 to December 2015 at Cyprus Rostov-on-Don propagation path. LFM transmitter worked around the clock with the transmission period of 5 min, and the frequency tuning rate of 100 kHz/s. Only frequency characteristics of regular 1F2 propagation modes in HF band were selected for the detailed analysis.

At this work the effects of medium scale traveling ionospheric disturbances (MS TID) on HF propagation in ionosphere are experimentally investigated. It is established that group delay and arrival angles in horizontal and vertical plane have significant quasiperiodic fluctuations due to temporal and spatial nonstationary of ionospheric plasma caused by influence of MS TID. It is shown that under the influence of medium scale traveling ionospheric disturbances the typical values of elevation angle variations reach 5°, the deviations of azimuth angle are 1°…2°. The maximum variations of elevation angle of the upper beams passing under the TID reach 10°, meanwhile azimuth deviations of Pedersen rays were 6°…8°. At the same time the lower beam group delay deviations are 0.2 ms, while for the upper reach 0.4 ms.

According to the measured frequency characteristics the evaluating of quasi-periods of the group delay and arrival angles fluctuations of the upper and lower extraordinary one-hop modes reflected from the ionospheric F-Layer at 0.9 of the maximum observed frequency (MOF) is performed. During the processing the power spectral density (PSD) variations of observed propagation characteristics of HF waves were estimated. Besides the quasi-periods of TIDs were found. It is shown that the PSDs of group delay disturbances and arrival angles disturbances similar to each other and contain the maxima for the frequencies in the intervals of the values of 26…38 MHz, 59…72 MHz and 110…130 MHz.

The most probable values of fluctuation quasi-periods were found for each obtained characteristics. For this purpose, for each day, the power spectral density estimates were made in increments of 10 minutes for the 160 min long data samples. According obtained data the histograms of distributions quasi-periods of HF propagation characteristics fluctuations were made. It is established that at 0.9 of maximum observed frequency the typical fluctuation periods are 15…18, 25…30 and 55…60 min.

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