ИСТИНА

The relation between activity levels at different layers of the outer atmosphere of stars provides information on impact of magnetic fields of various scales. Indices of the chromospheric and coronal activity are analyzed together with data on photometric variability of late-type stars. The bulk set of considered stars belong to BY Dra-type and they are characterized by the same relationship between levels of the chromospheric and coronal activity. But there is some number of the younger stars with activity levels close to the saturation. From the other side some of stars possess low chromospheric activity and their coronal activity is much higher than that on the Sun. For these stars activity of the outer atmosphere is compared with the relative area of spots responsible for the rotational modulation. There are evidences that the coronal X-rays is only associated with a high value of the relative spot area. This means that during the evolution of activity the coronal radiation related to local magnetic fields changes slowly, while the chromospheric emission associated with large-scale structures of magnetic fields is strongly attenuated.