MONITORING OF REGULAR AND SPORADIC IONOSPHERIC VARIATIONS ON THE SINGLE-HOP HF RADIO PATHS

• Published in: Radio physics and radio astronomy
• Main Authors: A. I. Reznychenko, A. V. Koloskov, Y. M. Yampolski
• Format: Article in Journal/Newspaper
• Language: English; Russian; Ukrainian
• Published: National Academy of Sciences of Ukraine, Institute of Radio Astronomy 2018
• Subjects: ionosphere; solar terminator; radio path; solar activity; magnetic storm; Astronomy; QB1-991; Norway; Tromsø
• Online Access: https://doi.org/10.15407/rpra23.04.266; https://doaj.org/article/e6dc015e3214484ea345f2b85cee38af

Purpose: Diagnostics of regular and sporadic ionospheric variations using coherent systematic monitoring of spectral characteristics of the probe HF signals on the inclined singlehop radio paths. Design/methodology/approach: Two HF receiving stations located at the Low Frequency Observatory of the Institute of Radio Astronomy, National Academy of Sciences of Ukraine, (Martove, Kharkiv region) and in Tromsø (Norway) were recording the signals at 9.996 MHz radiated by the radio station of the Exact Time and Frequency Service during the entire year of 2013. We estimated variations of the intensity and Doppler frequency shift (DFS) of the probe radiation derived from the power spectra recorded in the both observation points. The time series of these characteristics of the signals were compared with the independent estimates of the critical frequencies of the F2 ionospheric layer, as well as with indices of solar and magnetic activity. The correlation relationship between the time series were found. Findings: Systematic coherent measurements of spectral characteristics of the probe HF signals on two single-hop radio paths (high- and mid-latitude) have been made. The regular (background) variations of the diurnal dependences of intensities and DFS, caused by changes under the illumination conditions of the examined radio paths during the full annual cycle of observations, have been investigated. An empirical dependence between the moments of characteristic changes in DFS, “radio-sunrise” and “radio-sunset” with the solar terminator passage at various altitudes in the midlatitude and polar ionosphere was determined. Polar day conditions and growth of absorption in the midday and afternoon play the determining role for the high-latitude radio path in summer. An index characterizing the time interval when the signals propagate below the maximum usable frequency (the duration of the “radio-day”) is proposed. For the disturbed ionospheric conditions, the 27-day variations in the “radio-day” duration and the behavior of the ...