Авроральные явления - 73 : материалы наблюдений Полярного геофизического института за 1973 г. / Акад. наук СССР, Кол. фил. им. С. М. Кирова, Поляр. геофиз. ин-т ; [редкол.: Б. Е. Брюнелли (отв. ред.) и др.]. - Апатиты : Кольский филиал АН СССР, 1976.

5 w i t h increased activity are linked with first half arid the final days of the Bun revolution. Somewhat in the middle part,about the third quarter of the revolution a quiet period began. This quiet period exists at all Sun revolutions during the whole year gradually shirting to the initial days. High activity region on the graph has the wedge-shaped fo r m (cut b y the graph frame) starting from the beginning of the year and gradually narrowing to summer. In the second half year new active sequences develop between 19-th and 26-th days of revolution and near the 4-th.- 8 -th days. So in the first half year long systematically repeating active period exists and is replaced by a quiet one. Analysing active periods magnetograms one can find the parts whe n activity increased. These parts construct their own recurrent sequences. Four sequences are placed in the table on page 1 . Three of them,A,B and D exist only at the beginning and at the end of the year,but not in summer. The forth sequence С is observed continuously.during the whole year the latter sequence includes severe and moderate disturbances and it is typical that a quiet period exists before it. As a rule rather a long disturbed period begins from sequence C. Sequence D consisting of two branches and Dg mostly develops during disturbed periods when previous acti vi t y connected with sequence 0 is not vanished. These sequences are accompanied by a considerable increasing of activity. The first six members of sequence are the most severe and long storms of the year. The seventh member corresponding to a mode- X’ate disturbance is considered as the ending of this sequence. Sequence consists of storms developed on disturbed background and similar to D. they take place on the last days of the revolution. The members of sequence gradually shifts to the later days of the revolution when sequence Dg breaks this tendency. A long disturbed period follows sequence storms. Perhaps some a d d itional,not marked sequences existed du ring that period,however a ve r y high level ol' the disturbance makes their distingui shing difficult. A n intensive disturbance wh i c h arised during the last 24-2? days of the revolution continues up to approximately forth day of the next period. A compa rab l y small reducing of activity level is followed b y its new increasing which is marked in the table as sequence A. The fifth and partly the third members of the se quence A^ are marked as doubtful because a clear activity reducing before it is ab sent. Nevertheless the next members and especially ' 15.VH disturbances are quite evi dent. Sequence A^ corresponds to the same sun longitudes as in case of A ^ . The sequen ces in the Table are marked differently because in summer the row is interrupted and in August disturbances do not appear. Besides the disturbances of new sequence (A~) differs in character from if disturbances A^ developed in disturbed period and can be discovered only as amplitude increasing,disturbances A^ develop as a rule on a quiet background. Sequence ІЦ consisting of 5 members is not clearly developed,it begins from ra ther moderate disturbances seen on disturbed background. But the last two Diem bers of the sequence are comparably intence storms of 1-2 and 26-30 of April. A new sequence corresponding to the same Sun longitudes develops in autumn after comparably long in terval when the disturbances are absent. The disturbances of the sequence are rather moderate but arises on a quiet background. The seasonal v a r iation of geophysical activity is given on fig. 2 . Fig.2a shows average monthly value variation of hourly x'g. Magnetic activity has two maxima i highest - in March and the lowest one - in October. Up to the summer months - July and August the average Гу reduces to the half of April maximum value. This fact is marked in calendar (3?lg,1) descriptions an active part of 27 days period was conti nuo u s l y reducing fr o m the beginning of the year up to summer months. The intensity