Аскаплоты советских станций за 1984 год : (оперативно-информационный материал) / Акад. наук СССР, Кол. фил. им. С. М. Кирова, Поляр. геофиз. ин-т. – Апатиты : Кольский филиал АН СССР, 1990.

14 Averaging hee been done for 5 days which la similar to 1983. The similarity of сигѵез is rather good and the correlation coefficient equals to 0.6. Figure 5 gives oyolio variations. The solar activity was still decreasing but it did not reaoh the previous minimum of 1975-1976. In 1984 there started a decrease of auroral activity and the maximum of 1983 has become evident. The three auroral maxima for 1972-1984 make it роввіЪІѳ to define the periodicity of auroral adtivity which equals to 4.5 years. Similar but a more longer periodicity (5-6 years) was distinguished earlier /10/. Annual average level of magnetic activity in 19B4 has not practically changed as compared with 1983. There appeared a difference between cyclic variations of auroral and magnetio activity which were nearly synchronous during the previous period. This issue opens arranging the data on long-period trend of the activities considered. These data were obtained from the 11-year sliding averaged data. This teohnique provides both dismissing of 11-year variations and distinguishing either more prolonged cycles or tendencies to their appearance. Figure 6 presents the data for three years only, thus there is no reason to make any conclusions yet. Though it can be marked that there is a tendency to some increase In the 21st cycle for solar and magnetic activity Figure 7a displays the seasonal variation. The present year is characterized by a peouliar absence of dependence of magnetic and auroral activity seasonal variations on the mean values of Wolf numbers; the maximum of Wolf numbers was observed in the first half of the year, whereas their deep minimum was registered in its second half. Magnetic and auroral activities have seasonal variation reaching equinoxial maxima in summer and in winter. Seasonal variations for,2 Kp are more smooth. The autumn maximum is higher than the spring one for both magnetio and auroral activities though there is observed a deep minimum for Wolf numbers in autumn (the northern hemisphere). Mean seasonal variations foy 1972-1984 (Figure 76 ) are manifested only for magnetic activity with the maximum at the equinox, note that the spring maximum is higher than the autumn one. There are no seasonal variations for Wolf numbers and the PA index. Figure 7b presents the curves denoting the difference between the seasonal variations (1984) and the mean values for 13 years. During the considered year the auroral activity was lower than the mean value (see Figure 5) and auroral curves of difference show large negative and small positive values in the first and the second halves of the year, respectively. The situation was quite oontrary for the solar activity, viz. the first half of the year was characterized by small positive values, whereas the second half was marked by large negative values. Sinoe the mean level of magnetic activity remains high, as compared with decrease of solar and auroral activity, then its differences are always positive. Since there are no seasonal variations for FA and Wolf пшпЬѳгз for 1972-1984, thus Figure 7! b nearly reflects the character of curves presented in Figure 7a. The ееазопаі variations of magnetic aotivity do not coincide with these given in Figure 7a due to the effect of the mean seasonal variation. During the first half of the year there were observed variations about relatively small positive values; during the second half the difference increased and the amplitude of the variations sharply fell down (Figure 7B ) „