Radio Physics and Radio Astronomy (Mar 2019)
COMPARATIVE ANALYSIS OF GEOMAGNETIC DISTURBANCES IN THE ODESSA MAGNETIC ANOMALY AREA IN THE 24TH SOLAR ACTIVITY CYCLE
Abstract
Purpose: The main oscillation periods of the geomagnetic field perturbation level in the Odesa magnetic anomaly area are studied by the data observed at the “Odesa” geomagnetic observatory within the 24th solar activity cycle. The work is purposed to search for distinctions and similarity in manifestation and properties of short-term and long-term geomagnetic quasi-periodical variations under the conditions of anomalous, at the “Odesa” geomagnetic observatory, and poorly anomalous, at the “Kyiv” geomagnetic observatory, geomagnetic fields. Design methodology/approach: The data of high-time resolution digital magnetometers were used. Search for the fluctuation periods was made by the rapid continuous wavelet transform and the short-term Fourier transform (STFT). For the selection and subsequent separate analysis of fluctuations corresponding to different periods and spectral regions, the band-pass Fourier filtering was used. Findings: The change of periods of solar diurnal variations of geomagnetic field (24, 12, 8, 6 h) during the magnetic storms is determined. The shortest periods, 2 h and less, showed up in the “Odesa” geomagnetic observatory data. By the observations in the “Odesa” observatory, the increase of amplitude of short periods (4-5 h) with time during 2008–2013 has been marked. The variations with periods 6, 8 h react upon geomagnetic disturbances by the smooth increase of amplitude. Periods 4-5 h are recorded during strong magnetic storms, and weak variations with periods less than 4 h often appear during weak magnetic storms. Period about 27 days prevails in the “Kyiv” geomagnetic observatory data, and that of about 37 days – in the “Odesa” geomagnetic observatory data. The changes of amplitude of solar diurnal variations of geomagnetic field during 2015 by the “Odesa” observatory data are determined for the subsequent comparing to the solar activity behavior. Conclusions: Generalization of results shows differences in behavior of the basic periods of geomagnetic activity in the Odesa magnetic anomaly area (the “Odesa” observatory) and under the conditions of the poorly anomalous geomagnetic field (the “Kyiv” observatory). At the “Odesa” observatory, the short periods show up more noticeably, less than 6 h. At the “Kyiv” observatory, the long duration periods prevail (from a few days up to a few tens of days).
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