ANALYSIS OF THE MAGNETIC STORMS CATALOG FOR MONITORING RADIO SOURCE FLUXE DATA WITH THE URAN-4 RADIO TELESCOPE IN THE ODESA MAGNETIC ANOMALY ZONE

L. I. SOBITNYAK , M. I. RYABOV , M. I. ORLYUK , A. L. SUKHAREV , A. O. ROMENETS , YU. P. SUMARUK , and А. А. PILIPENKO 1 1 Observatory “URAN-4”, Institute of Radio Astronomy, National Academy of Sciences of Ukraine, 1v, Marazliivska St., Astronomical Observatory, Odesa, 65014, Ukraine E–mail: ryabov-uran@ukr.net 2 S. I. Subbotin Institute of Geophysics, National Academy of Sciences of Ukraine, 32, Palladin Ave., Kyiv, 03142, Ukraine E-mail: orlyuk@igph.kiev.ua


Introduction
The "Odesa" geomagnetic observatory was founded by the Novorossiysk Imperial University, on the botanical garden area, at the beginning of the XX century. In 1936, it was moved to the village of Stepanivka (near Odesa) by the Odesa State University. After the World War II, the Observatory became to belong to the Institute of Geophysics. Since 1948 till 2010, the analog measurements of the Earth's magnetic field were made at the "Odesa" geomagnetic observatory. At the same time, the measurements of three elements of the magnetic field were recorded: horizontal component (H), vertical component (Z), and inclination (D), based on which the magnetic storms data were given in a tabular form [1]. Fig. 1 shows a monthly review of the magnetic field state in November 2003. The content of the catalog is presented in paper [2].

Catalog of magnetic storms
Using the "Odesa" geomagnetic observatory data, the magnetic storms catalog was made. This catalog issue for the 1987-1995 and 2000-2009 years include: the date and time of the beginning and the end of a storm, the storm duration, the amplitude of the magnetic field H, Z, and D components, and the characteristics of magnetic storms with the indication of the fissile periods. As an example, the observational data of the "Odesa" geomagnetic observatory for the period of January-March 2003 are given in Table 1. The total number of minor, moderate, strong and extreme storms are shown in Table 2 and Fig. 2.
The catalog was compiled to identify the reasons for the change in the space radio sources' flux level, according to the observations made since 1987 with the Odesa Observatory URAN-4 radio telescope of the Institute of Radio Astronomy of the National Academy of Sciences of Ukraine. The data on powerful radio source flux changes during the periods of extreme states of solar activity are given in [3]. Paper [3] also presents the results of calculating multiple correlation analysis models, which show the dependence of the radio source flux changes on the main indices characterizing the space weather state.

Magnetic anomaly zone
The "Odesa" geomagnetic observatory is located near the intensive magnetic anomaly. Since the dome of the geomagnetic field extends to the altitudes of about 90 km into the ionosphere layer, where the variation (rapidly variable) component of the geomagnetic field is formed, the regional magnetic anomalies can affect the manifestation of the geomagnetic field variability. When processing the long-term observations data, the magnetic anomaly influence on the geomagnetic activity was found. The map of the anomalous geomagnetic field distribution near the Odesa city is shown in Fig. 3.
To identify the magnetic anomaly influence on geomagnetic activity, the magnetic storms characteristics were compared according to the "Odesa" and "Moscow" (IZMIRAN, Russia) geomagnetic observatories data. The total duration of all magnetic storms throughout the year in Odesa is longer than in Moscow (see Fig. 4). Table 3 provides information on the duration of individual magnetic storms in the "Odesa" and "Moscow" geomagnetic observatories' areas for 1987-1995 and 2001-2003. Since 2017 till 2019, right in the center of the magnetic anomaly on the area of the Astronomical Observatory of the Odesa I. I. Mechnikov National University, the magnetic field variations were mea-  sured with the LEMI-008 precision flux gate magnetometer of the S. I. Subbotin Institute of Geophysics of the National Academy of Sciences of Ukraine. The measurements were made with a second resolution time. As a result, the data on rapid variability of the geomagnetic field H, Z, and D components, lasting for more than 1 year, were obtained. The dependences of the time-frequency wavelet spectra on geomagnetic storms of different strengths and caused by different active processes on the Sun have been studied. These properties (amplitudes of Fig. 2. Graphical representation of the number of magnetic storms in the catalog geomagnetic variations in the bands of individual quasiperiods, changes in quasi-periods over time and at the moments of storms, disturbances, and geomagnetic quiet days, changes in the spectral power density of time series with time that shows the "overlap" of different fluctuations for the same, quite short periods of time) are compared with the properties of fast geomagnetic variations obtained on the "Dymer" geomagnetic observatory area, Kyiv region, where the geomagnetic field is very close to normal. It is shown that there are significant differences between the type of digital spectra for the "Odesa" and the "Dymer", and between the properties of variations in the geomagnetic field. Thus, in the "Odesa" data, the short-period component of variations is more prominent, the fluctuations with periods of up to 4-5 min are reliably distinguished, and up to 3 minutes on low-noise days. These variations are often quasiperiodic during the geomagnetic storms. According to the "Dymer" observatory data, the quasiperiodic variations are mainly concentrated in the low-frequency region of digital spectra, in the period band of 12-30 min. Sometimes there are complex transitions of oscillation periods, which have a characteristic "grid" shape on the digital spectrum, usually in the bands of periods from 5 to 20 min, and usually observed at night and in the morning. However, this occurs quite rarely. Usually, the geomagnetic variations according to the "Dymer" observatory data become noisy in the band of periods less than 13 min. Thus, the "prints" of geomagnetic storms and disturbed days are different for the areas of anomalous field ("Odesa") and for a calm field Taking into account the fact that in the Odesa regional magnetic anomaly area there is the URAN-4 lowfrequency radio telescope (phased antenna array) of the decameter (10-30 MHz) wavelength range, the study of the relationship and differences between the ionosphere scintillations of powerful galactic and extragalactic radio sources (on a cloud of homogeneities) and the rapid variations in the geomagnetic field, since both of these phenomena are consequence of ionosphere processes. The Odesa Regional Magnetic Anomaly is a unique "natural laboratory" in Ukraine and studying its connection with the ionosphere will continue.

Ñonclusions
1. Using the "Odesa" geomagnetic observatory data, the catalog of the magnetic storms is made. This issue of the catalog for 1987-1995 and 2000-2009 include: date and time of the beginning and the end of a storm, the storm duration, amplitude of the magnetic field H, Z, and D components, the characteristic of magnetic storms.
2. The comparison of the magnetic storms duration recorded at the "Odesa" geomagnetic observatory is longer than that obtained at "Moscow" (IZMIRAN).
3. It is planned to create the catalog of magnetic storms according to the "Odesa" observatory data obtained for the entire monitoring period of space radio sources at the URAN-4 radio telescope in order to identify the manifestations of geomagnetic disturbances during radio astronomical observations and their contribution to changes in radio source fluxes at decameter waves.  Fig. 4. The total annual duration of magnetic storms according to the "Odesa" and "Moscow" geomagnetic observatories data 4. These studies will be supplemented by a comparative analysis of the characteristics of magnetic storms in the magnetic anomaly zone ("Odesa") with the data from some other magnetic observatories.
5. The complete content of the magnetic storms catalog will be presented on the website of the S. I. Subbotin Institute of Geophysics of the National Academy of Sciences of Ukraine and the Institute of Radio Astronomy of the National Academy of Sciences of Ukraine.