Petrov P. Activity of young solar mass stars.

The thesis is devoted to investigation of activity of young solar mass stars, manifested in variations of spectroscopic and photometric parameters and caused by different physical mechanisms - by the solar type magnetic activity and by accretion of matter on the stellar surface. The results of the thesis are based on the observational data collected by author in 1980s and 1990s at the 2.6-meter Shajn reflector, Crimea, Ukraine, and at the 2.5-meter Nordic Optical Telescope, La Palma, Spain. The size, temperature and life time of the large spotted region on the surface of V410 Tau are determined. The pattern of gas flows around classical T Tauri stars and the role of magnetic field in control of accretion and wind flows are revealed. The observed effects are compared to those predicted by the model of the magnetospheric accretion. Rotational modulation of the spectral features of accretion, caused by axial asymmetry of the stellar magnetic field, is discovered in RW Aur. Spectral variability of the fuors FU Ori and V1057 Cyg is investigated. Quasi-periodic variations in velocity and density of stellar wind is found in FU Ori. It is shown that the observed peculiarities of the optical spectra of the fuors cannot be described by the homogeneous accretion disk model.