On the peculiarities of manifestation of kG magnetic elements in observations of the Sun with low spatial resolution

Abstract

Abstract. On the agenda of modern astrophysics is the exploration of not only disk-integrated stellar magnetic fields but surface mapping of them. However, it is hardly possible to expect that spatial resolution better than some dozens or hundreds pixels over stellar disk will be achieved for this goal in the foreseeable future. Among other reasons this fact makes very important observations of the average and large-scale magnetic fields of the Sun, which can be naturally used for testing polarimetric measurements on other stars, especially on solar-type stars. In this study we explore different aspects of observations of solar magnetic fields (SMF) with low spatial resolution, including Sun-as-a-star observations, which are characterized by extremely low magnetic flux densities. Comparison of disk-integrated and spatially resolved Stokes observations of the Sun allow us to demonstrate how Stokes V profiles depend on the distribution of large-scale magnetic fields in the disk center. It is shown that center-to-limb variations of magnetic strength ratios (MSR) and area asymetries, most likely could be interpreted as the manifestation of kG magnetic flux tubes. We have made cross-calibration of the full-disk magnetograms obtained by space-borned SDO/HMI and by the ground-based STOP telescope, and pretty good agreement is found. Finally, the absence of significant systematic time variations of MSRs with solar cycle is demonstrated.