[2] The solar activity minimum is an important period of solar cyclicity. During this time the solar atmosphere is weakly disturbed by eruption of active regions. The general magnetic field of the Sun is determined by the large-scale structures. The northern and southern hemispheres of the Sun typically have magnetic fields of different polarities. The intensity of the magnetic field in the polar regions is much higher than the intensities of those at middle and low latitudes. At high latitudes, polar faculae appear. During the solar activity minima, the properties of the global magnetic field, i.e., of the magnetic field characteristic of the entire Sun, manifest themselves in a most pronounced way. This period is also important for the whole activity cycle because generation of the toroidal field of active regions is likely to occur from weak magnetic fields having a global nature. Nevertheless, no commonly accepted indices characterizing the condition of the solar atmosphere during this period are available at present. As a rule, the activity indices characterize the presence of the activity of sunspots or their derivatives. Their use for the investigation of the solar activity minima is not efficient enough for different reasons. First, the majority of indices relates to the region of sunspot formation and does not characterize the general condition of the atmosphere from one pole to the other. Second, the configurations of the large-scale fields during the sunspot activity minima considerably differ from the bipolar magnetic structures associated with sunspots. At high latitudes, an enhanced activity has been found to occur during the periods of sunspot activity minima, while the indices of the polar activity have not been studied thoroughly enough.
[3] In this paper, a number of new indices characterizing the condition of the solar atmosphere during the period mentioned above are suggested. In part, these indices were obtained from synoptic Ha charts [Makarov and Sivaraman, 1989; McIntosh, 1979; Vasil'eva, 1998]. Other indices were obtained in studies of bright calcium points at high latitudes and variations in the rotation velocity of the magnetic field sector structure.
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