Geophysical research: article

Аnnotation: This research deals with the study of seasonal variations of the Earth's magnetic field using the changes in the intensity of its diurnal variations. The initial data were recorded at the Bavra and Gyulagarak observation points of the of the full module of the geomagnetic field vector (Republic of Armenia). A comparison is made between the variations identified from the data registered at these points and the variations that appear in the data from the magnetic observatory Chambon-la-Foret (France), which is close in latitude. They are also compared with geomagnetic variations identified using the global geomagnetic activity indices. The comparison results show that, according to geomagnetic observations, annual variations are distinguished, caused by the ionospheric current system and expressed by the maximum intensities of diurnal variations in the summer months and minimums in the winter season. According to the geomagnetic activity indices, semi-annual variations of magnetospheric sources with characteristic maxima during the spring and autumn equinoxes are distinguished. Comparison of solar-diurnal variations between the Bavra and Gyulagarak station data showed the similarity of their amplitudes in the summer. However, the duration of the maximum intensity period of diurnal variations at Gyulagarak station data is one month longer than that of the maximum intensity period of diurnal variations at the corresponding data from Bavra station. The revealed temporal characteristics of seasonal variations in the geomagnetic field are consistent with existing ideas about geomagnetic variations due to the influence of external sources. Comparison between the annual variations revealed by observations on the territory of Armenia and the ones according to the data registered at the Chambon-la-Foret observatory showed a similarity of the main characteristics of the studied variations. The noted circumstances can be considered as a scientific justification for the feasibility of creating a magnetic observatory in Gyulagarak.