Аскаплоты советских станций за 1976 год : (оперативно-информационный материал) / Акад. наук СССР, Кол. фил. им. С. М. Кирова, Поляр. геофиз. ин-т. – Апатиты : Кольский филиал АН СССР, 1989.

12 Auroral PA index. The index of auroral activity calculated on the basis of ascaplots was suggested in /10/. It equals to PA = N*K (Ф Л ), where К is the number of blackened squares within the time interval, and Кis the coefficient depending on the corrected geomagnetic coordinates. The connection between N and the auroral magnetic index AL for midnight hours was determined in /10/ from ascaplots of 35 Stations during IGY /1,2/. Using these data the dependence of К-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 К-index was calculated for midnight auroras 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 PA index being lineary proportional to the energy of auroral electrons of the auroral oval /10/. This permits to make any arithmetic operations with PA index, such as averaging, without losing the physical content. Table 2 includes PA values for each day in 1976. 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 trough in the Table denotes absence of obser vations on that day at local midnight. Auroras registered at cloudy conditions were taken into account in calculation of 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. The correlation coefficient of PA value obtained according to different procedures is 0.7. According to the new procedure, on the average, the value of PA index is higher by a factor of 1.3. Auroral activity in 1976. Figure 3 presents PA index variations for each day in 1976. The points denoting gaps in observations are linked by dashed lines. The same figure contains corresponding changes of the diurnal Kp index sum (the scale down wards). In 1976 4 stations operated in the Antarctic region, the data from three of then (Novolazarevskaya, Molodezhnaya and M y m y ) have been used for calculation of PA index. Like during the previous years /5,6/ general similarity between auroral and magnetic activity variations is observed. Certain discrepancy may be accounted for by much worse representativity of the PA index. As has been already shown it is determined by auroral conditions during 4 hours around the local midnight for each station. So if the magnetic disturbance appeared not during this time interval then it was not included into PA index. Magnetic activity is presented by the diurnal Kp sum, i.e. the mean value of disturbance, and when the number of stations is limited certain discrepancy of PA relatively to Kp index may arise, namely, PA index may decrease if the magnetic bay did not coincide with the obtained observational interval and vice versa it may be higher if during the day only a single disturbance was observed which coincided with the local midnight at the station. Smoothing of