Sumaruk Y. Spatial-temporal distribution of secular variations of the geomagnetic field from external and internal sources.

The thesis is designed to study the spatial-temporal distribution of secular variations of the geomagnetic field from external and internal sources and to evaluate the contribution of these sources depending on the parameters of solar and geomagnetic activity based on data from geomagnetic observatories around the world as well as on those from international centers investigating solar-terrestrial communications. Studies of secular variations of the geomagnetic field in different regions of the Earth's surface have shown the presence of short-term, cyclic and long-term changes. The sources of short-term and cyclical changes are ionospheric and magnetospheric currents associated with solar activity. Long-term secular variations have sources both outside and inside the Earth. Long-term variation from internal sources changes little over time. Its magnitude from external sources varies according to the quasi-sinusoidal law with a change in solar activity. For the first time a method of separating a secular variations of the geomagnetic field from external and internal sources was developed. Due to that, the contribution of external sources to the secular variation, which depends on solar and geomagnetic activity, is calculated. In turbulent periods, this contribution is proportional to secular variation value. Key words: magnetic field of the Earth, secular variations, solar and geomagnetic activity, geomagnetic observatories, magnetic storms.