Аскаплоты советских станций за 1983 год : (оперативно-информационный материал) / Акад. наук СССР, Кол. фил. им. С. М. Кирова, Поляр. геофиз. ин-т. – Апатиты : Кольский филиал АН СССР, 1990.

II the forms (corresponding to the international classification) an well aa brightness of forms (W - weak, M - mean, В - bright). Two circles denote duration of observations, the left circle means that the observation period was more than 15 minutes shorter than that denoted by the right circle. The indices, by which the balls of activity are calculated, are given at the top of the Table. Indices 1-3 correspond to the first ball, whereas indices 4-6 and 7-9 correspond to the second and third ball, respectively. For several forms occuring simultaneously the index is calculated by the most important form plus one. For example, if during more than 15 minutes a weak homogeneous arc (HA) and a weak radiant band (RB) were observed, 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 motion) + 1 (occurence of other auroral forma) = 9. Thus, a very bright homogeneous arc observed during the whole interval (half an hour) gives 2 balls, whereas a mere fact of appear ance of a corona corresponds to the same activity. Such estimations of auroral activity in balls is connected with peculiarities of development of the auroral substorm. According to /8/ the periods of no disturbance or absolutely quiet periods homogeneous arcs (HA) and bands (HB) with bright ness gaining sometimes 2 balls (these are not the balls of activity but the balls of brightness according to International Classification) may be observed along the compressfed oval. On the dayside separate rays or weak radiant arcs are usually seen. A weak substorm causes increasing of bright ness, appearance of curves, i.e. transition of arcs into bands and appear ance of radiant structures. 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 ascaplotting is connected with the peculiarities of substorm development and, to some extend, characterizes the intensity of the eubstorm. Figure 2 presents nn example of ascaplots. The numerals I-XV show various possible situations. In the.given example the camera did not operate until 13.10 UT. Observations began at 13.30 UT, auroras were absent, cloudi ness with rents was in the north and in the zenith (I). During the next half-an-hour interval (II) auroras were also absent, oomplete cloudiness was in the north and in the zenith, cloudiness with rents was in the south; III and IV correspond to the time interval of complete cloudiness covering the whole ekyj 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 only in the north, local geomagnetic midnight. IX shows that auroras again shifted to the zenith and their activity gained 2 balls, no clouds 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, acltlvity of 3 balls, neither auroras ncr clouds in the south, XII: no auroras were observed in the north, probably because of cloudiness with rents, the activity in the zenith reduces to 2 balls. XIII: auroras of not moi'e than