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.

I I 15 min a weak homogeneous arc (HA) and a weak radiant band (RB) were observed in the sky, the index equals to: 6 (radiant band) + 1 (occurence of another form) = 7 that corresponds to the third ball of auroral activity. One is added for a quick motion of the main auroral form. For example, a bright quickly moving radiant band existing less than 15 min with occurence of other forms gives: 7 (bright radiant band) + 1 (its quick moving) + 1 (occurence of other auroral forms) = 9« Thus a very bright homogeneous arc observed during the whole interval (half an hour) gives 2 balls, whereas a mere fact of appearance of a short-living corona corresponds to the same activity. Such estimation of auroral activity in balls is connected with peculiar ities of development of the auroral substorm. According to /8/ during periods of no disturbance or absolutely quiet periods there may be observed homogeneous arcs (HA) and bands (HB) with brightness gaining sometimes 2 balls (these are not the balls of activity but the balls of brightness according to International classification) along the compressed oval. On the dayside separate rays or weak radiant arcs are usually seen. A weak substorm causes increasing of brightness, appearance of curves, i.e. transition of arcs into bands and appearance of radiant structure. A strong substorm is characterized by an apparent breakup, i.e. quick motion of auroras, collapse of forms, appearance of coronas and pulsating auroras. Thus, the series of auroral activity used for ascaploting is connected with the peculiarities of substorm development and,to some extend, characterises intensity of the substorm. Figure 2 presents an example of ascaplots. The numerals I-XV show various possible situations. In the given example the camera did not work until 13.30 UT. Observations started at 13.30 UT, auroras were absent, cloudiness with rents was observed in the north and in the zenith (I). During the next half-an-hour interval (II) auroras were also absent, complete cloudiness was observed in the north and in the zenith, cloudiness with rents in the south; III and IV correspond to the time intervals of complete cloudiness covering all the sky; V denotes cloudiness with rents in the south and in the zenith, and no clouds in the north. Auroras in the north appeared at 16 UT (VI), there were no clouds in the zenith and cloudiness with rents in the south. VII shows no clouds in the sky, auroras were observed in the north and in the zenith. VIII marks that the sky was clear, auroras were seen only in the north, local geomagnetic midnight. IX shows that auroras again shifted to the zenith and their activity gained 2 balls, no clouds were seen in the south. X: auroras spread all over the sky, the activity in the zenith was equal to 3 balls. XI: auroras were in the north and in the zenith, activity of 3 balls, neither auroras, no clouds were observed in the south. XII: no auroras were obser ved in the north, probably because of cloudiness with rents, the activity in the zenith reduced to 2 balls; XIII: auroras of not more than 1 ball were observed in the north and in the zenith, no clouds in the south. XIV: the sky is cloudless, no auroras, moon lighting. XV: the situation is similar, but the ascafilms turned out to be of bad quality due to technical reasons (bad development of this part of the role, breaks of automatic operation, etc.). The described example presents all situations one may encounter in ascaplots.