Аскаплоты советских станций за 1981 год : (оперативно-информационный материал) / Акад. наук СССР, Кол. фил. им. С. М. Кирова, Поляр. геофиз. ин-т. – Апатиты : Кольский филиал АН СССР, 1989.

13 with April and October equinoxial maxima is mostly remarkably manifested in magnetic activity. The winter minimum is more lower that the summer one. A small rise of magnetic activity is recorded in July-August. In 1981 maxima in solar activity are also observed at equinoxial months as well as comparatively lower minimum in July; this, minimum coincides with the minima of magnetic and auroral activity. Figure 5 6 displays the mean seasonal variation of the same parameters for 1972-1981, i.e. for ten years. Similar to separate years (see /5/) the seasonal variation of auroral activity is not observed. Solar activity is higher in October- November; for all the rest months it is lower than its mean value. Magnetic activity manifests a definite maximum in March-April and it is much weaker in October. Figure 5 в shows difference variations for each month between the values for 1981 (Fig.5a) and the mean values for 10 years (Fig,56 ) for the same parameters of activity. Since magnetic and solar activities in 1981 are higher,then the difference is mainly positive; note the difference variations recur the seasonal variation of activity observed in 1981 (Fig.5a). The same situation (but for a lower amplitude) is observed for auroral activity. Figure 6 presents cycle variations of auroral, magnetic and solar activity obtained by data averaging for 12 months of each year. In the issue "Ascaplots of 1980" /5/ auroral activity values are given without correction of auroral registr ation under cloudiness; thus the cycle PA variation given in Fig.6 differs from the data cited in "Ascaplots of 1980". Cycle variations of magnetic and auroral activity turn to be synchronous after correction. The main feature of these variations is two maxima during the 11-year solar cycle. The first maximum is observed on the fall of solar activity (the years 1973-1974, as well as PA rise in 1981 after the start of decreasing of the Wolf numbers); the second maximum coincides with the growth phase of the number of aolar spots (1978). The minimum of solar activity coincides with the minimum of magnetic and auroral activity. Similar results have been obtained in /10/.