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.

12 the forma (corresponding to the international classification) as well as brightness of forma (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 homogeneoua 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 ia 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 forms) = 9. Thus, a very bright homogeneous arc observed during tho whole interval (half an hour) gives 2 bells, whereas a mere fact of appear- ence of a corona corresponds to the same activity. Such estimations of auroral activity in balls ia connected with peculiarities of development of the auroral substorm. According to /8/ the periods of no disturbance or absolutely quiet periods homogeneoua 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 compressed oval. On the dayside separate rays or weak radiant arcs are usually seen. A weak substorm саизез increasing of bright ness, appearance of curves, i.e. transition of arcs into bands and appear ance of radiant structures. A strong subatorm 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 зо'че extend, characterizes the intensity of the substorm. Figure 2 presents an example of aaoaplots. The numerals I - X V 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, cloudl» ness with rents was in the north and in the zenith (I). During the next half-an-hour interval (II) auroras were also absent, complete cloudiness wa3 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 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 (VT), there were no clouds in the zenith and cloudiness with rents in the south. VII shows no clouds in the sky, auroras ware observed in the north and in the zenith* VIII marks that the sky was clear, auroras were only in the northy local geomagnetic midnight. IX shows that auroras again shifted to the zenith and their activity gained 2 balls, no clouds in the south. X: aurorae 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, acitivity of 3 balls,, neither auroras псе - 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 more than