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.

6 of storms in March, and April is higher than at the beginning of the year and that's w h y Гр increased f r o m January to March. Maximum during September equinox is connected w i t h the second recurrent branches appearance marked in the calendar and in the table. As an illustration of activity distribution during the year may be used the l ength of the paper on which month magnetic records can be p l a c e d ,because the higher a c tivity needs more paper for its presentation, i'ig .3 shows the variation of these paper lengths. It looks rather unexpected that such a measure gives more smooth yearly v a r i a t i o n than r^-index. Fig.2b presents a seasonal variation of ionospheric activity destrioution accor ding to calendar (Fig.1) data. The variation forms a simple wave with minimum in sum me r and maximum in winter.complicated b y additional maxima connected with corpuscular precipitations increasing during equinox. The variation of aurora intensity in different emissions is given in Fig.2c. In order to omit dark period as in previous our books here is used only measurements made near midnight. The character of variation is not similar to Fig.2a and Fig.3 5 the difference may appear because the duration of disturbance in this case is not taken into account and besides the disturbance variation at different fixed moments of the da y may be various. Daily variation of geophysical activity ab different seasons is given in Fig.4. Fig.4a gives daily variation of hourly r^. Geomagnetic activity is maximal in spring (February - April) and minimal in summer(May - July),it corresponds to Fig,3. Daily activity variation in spring has a sharper and higher maximum than in other seasons and it takes place exactly at geomagnetic midnight. Other seasons have daily maximum wider and nat urally - lower. A ctivity minimum is observed during late morning hours which are characterized b y generation of pulsation or irregular fluctuation,but not appearance of positive or negative bays. The curve of activity variations during summer desplays an additional and quite evident minimum at evening hours. In spring and autumn this m i n i m u m is not so evident. Fig.4b presents the variation (in kR) of luminosity of the main aurora emissions during night hours. The v a riation of 557?& emission has one wide maximum around geo magnetic midnight. The variation of 4276 and 6300%. emissions show not only midnight's maximum but two additional ones placed some hours apart from midnight. This peculia ri t y was marked in materials of 1972 /4/ also. Daily variation of ionospheric activity obtained f r o m calendar (Fig.1) data is given in Fig.4c. The disturbance is maximal in winter and at night hours. Daily vari ation of disturbance can be described as an abrupt increasing of disturbance at eve ning hours followed b y a wide m aximum and gradual reducing of activity towards the beginning of the day. In summer the amplitude of activity daily v ariation is smaller than in winter but still rather big,but in spite of the fact that the ionosphere is sunlit during the whole twenty-four-hour period. In summer ionospheric disturbance m inimum takes place at morning and evening hours with significant activity increasing n e a r noon. In other seasons these two m axima are not cl^ar and the graph has the form of a wide minimum around noon. In the Russian text the description of activity behaviour during different months 01 the year are given. One can see how typical pecularlties mentioned in the above description desplay in certain disturbances occured in 1973»