engleski

Properties of the solar velocity field indicated by motions of sunspot groups and coronal bright points

The solar dynamo is a consequence of the interaction of the solar magnetic field with the large scale plasma motions, namely differential rotation and meridional flows. The main aims of the dissertation are to present precise measurements of the solar differential rotation, to improve insights in the relationship between the solar rotation and activity, to clarify the cause of the existence of a whole range of different results obtained for meridional flows and to clarify that the observed transfer of the angular momentum towards the solar equator mainly depends on horizontal Reynolds stress. For each of the mentioned topics positions of sunspot groups and coronal bright points (CBPs) from five different sources have been used. Synodic angular rotation velocities have been calculated using the daily shift or linear least-square fit methods. After the conversion to sidereal values, differential rotation profiles have been calculated by the least- square fitting. Covariance of the calculated rotational and meridional velocities was used to derive the horizontal Reynolds stress. The analysis of the differential rotation in general has shown that Kanzelhöhe Observatory for Solar and Environmental research (KSO) provides a valuable data set with a satisfactory accuracy suitable for the investigation of differential rotation and similar studies. A significant correlation was found between the solar equatorial rotation speed and indices of the solar activity, for both tracers. Different CBPs and sunspot groups results for the meridional flows are consistently interpreted. The analysis of the horizontal Reynolds stress, by both tracers, showed transfer of angular momentum towards the solar equator, which is consistent with the observed solar differential rotation profile. The results presented in the thesis are original scientific contributions primarily fundamental in nature, but a part of the research also has possible applicative potential for the use of dynamo modelling.

Sunspots ; differential rotation ; velocity fields

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