It is difficult to prepare an invited paper on topics which are ABC for any specialist in Solar Physics. I considered my task as a systematization of a lot of information about cyclic and secular variations of solar activity rather than an account of new striking results in order to illustrate a certain concept. I beg your pardon in advance for possible defects in my report and for lack of time to quote all related papers. Philosophy ASPECTS, CONCEPTS, INDICESOne can speak about three aspects of the study of solar activity, as a whole, although usually no essential difference is made between them. The frequency-time aspect of solar activity study involves the consideration of a set of time variations in different solar activity indices and the determination of the power spectrum of quasiharmonic and cyclic variations. The spatial aspect implies the study of the spatial distribution of solar activity phenomena and, in particular, the clearing up of the degree of homogeneity or inhomogeneity in the distribution of various solar activity indices in latitude and longitude. The study of the significance of individual phenomena, which depends directly on the phenomena lifetime, reflects the importance of these investigations.The basic concept crystallized from results of papers done in the past 20 yr, is associated with the division of various solar activity phenomena and indices charac terizing the former into two large classes. This idea was proposed for the first time by Kopecky (1958). To the first class belong indices which predominantly reflect how frequently new formations appear on the Sun. A nearly uniform distribution in longitude and a relatively low concentration in latitude is typical for them. The main time variation is the 11-year cycle. Time variations in the spatial distribution pattern are influenced by the differential rotation. The indices pertaining to the second class contain information on phenomena importance. Their spatial distribution corres ponds to a substantial inhomogeneity in longitude (the presence of so-called active longitudes), and the concentration in the low latitude region below 20°. Time variations of these indices mainly are represented by a secular (80-90 yr) cycle. It is remarkable that the spatial distribution of indices is not influenced by the differential rotation, but it rotates rigidly with a constant angular velocity. The presence of the two classes requires a different approach to indices which contain frequency and importance aspects of the phenomena. The mixing of these factors, as a rule, leads to uncertainty and sometimes even to contradictions in the results, depending strongly on data processing.

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On the basis of a review of data on the effective cross-sections of particle interactions, computations of the effective electron-neutron interaction, of the cross-section values for H, H,, and He were carried out in the range 0.8 ~< ~' ) ~< 1.7 and 2.5 ~< IogPg ~< 6.5. The mean cross-sections for the solar mixture used by Zwaan were computed (see Table ll). Using these results, the values of the electric conductivity and of its anisotropy coefficient were computed (see Tables VII and VIII), as well as other auxiliary quantities. The conductivity values obtained are in the range from 5 • 10 ' to 5 • 10 t2 CGSE units for the assumed physical conditions.

The results of observations of the umbral flashes in two sunspots are reported. The sunspots differ in their morphological properties (evolution rates and activity levels) and in observation conditions (heliocentric distances). The oscillation parameters of the two sunspots do not coincide. The most significant differences are pronounced in the phase relations and amplitudes of observed oscillations.

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