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.

13 1 ball were observed in the north and in the aonith, no clouds in the south. XIV': the sky ie cloudless, no aurorae, moon lightening. XV: the situation is similar, but the ascafilms turned out to be of poor quality due to soma technical reasons (bad development of this part of the film, breaks of automatic work). The described example presents all the situations one can encounter in ascaplots. Auroral PA index. The index of auroral activity calculated with the help pf ascaplots was suggested in /9/. It equals to:PA ■ N )8 where N is the number of blackened squares within the time interval, and К ia the coefficient depending on the station's latitude. The connection between N and the auroral magnetic index AL for midnight hours was determined in /9/ from ascaplots of 35 stations during IQY /1,2/» Using these data the dependence of the K-coefficient on the latitude was obtained for two longitudinal intervals. This allows to adjust the data of the stations located at different latitudes to a common value. Since the K-indax was calculated for midnight auroras, the PA index is estimated only for a 4-hour interval in the region of the local geomagnetic midnight. AL scales are chosen so that the corresponding values of the PA index be linearly proportional to the energy of auroral electrons of the auroral oval /9/. This permits to make any arithmetic operations with PA index, such as averaging, without losing of physical content, Table 2 includes PA values for each day of 1984. For a separate station PA can be determined only for a 4-hour interval which may not coincide with the maximum of auroral activity. That is why Table 2 presents PA values obtained by averaging the indices of all the stations operated during that day. The numeral in brackets following every index gives the number of operating stations the data of which were averaged in calculating the index. The gap in the Table denotes absence of observations on that day at local midnight, Auroras registered at cloudy conditions ware taken into account in calculations of the PA index» This change increases the representativity and statistical veracity of the data, but on the other hand, this leads to a rise of the PA average value. Auroral activity in 1984« Figure 3 presents diurnal values of the PA index and Kp for each day in 1984, This graph features auroral and magnetic activity and may serve as a basis for preliminary selection of the data. The dashed line joins the points denoting absence of observations. Such cases were particularly often in May and August. Note that PA із determined only from midnight hours, thus even if are no data in Table 2 or Figure 3 auroras might be observed during other hours of the local time. The number of observational stations were small; in most cases PA is determined by a single station that is non-representative. 80 per cent of PA events in 1984 were determined by a single station, whereas 1 6 per cant and 3 per cent by two and three stations, respectively; and only one event was determined by four stations* Similar to the previous years the degree of interconnection between auroral and magnetic activity increases when the data are averaged. Figure 4 presents variations of magnetic and auroral activity for February- April when the cases of defining PA by several stations were numerous.