Авроральные явления - 78 : результаты работ по программе Международного года исследований магнитосферы : материалы наблюдений Полярного геофизического института за 1978 г. : (оперативно-информационный материал) / Акад. наук СССР, Кол. фил. им. С. М. Кирова, Поляр. геофиз. ин-т ; [отв. ред. Б. Е. Брюнелли].

5 electron type. The hydrogen emission has maximum at evening h o u r s . The intensity of red oxygen 630nm emission is unusually high in the year. The h i g h and low activities last for some days (see Calendar Fig.2)} their dist ribution is repeated at the next solar rotation forming the recurrent sequences. The sequences were clearly seen also during the previous years of the decreasing solar activity. During this year the tendency of repeatition is less pronounced but still exists. A n additional evidence of recurrent tendency existence can be obtained from Table 2,where daily mean rH are given. Days with sharp increasing of rH comparing to the previous day are also marked. These days and the days with magnetogram more complicated than at the previous day are listed in Table 3 in form of four sequences. The position of two of them in relation to solar rotation (or heliographic longitude) is rather constant whereas the other two are gradually drifting towards the later days of the Bartel's rotations. The repeatition period of the first two is 27 days as usual,ror the last two the period exceeds 28 days. The active regions on the Sun which are responsible for the first and the last two are placed in different helio graphic latitudes. The connection between the distribution of high-latitude geomagnetic activity and the sector structure of Interplanetary Magnetic Field (IMF) was demonstrated in the previous volumes with the data on the years of solar activity decreasing. It was noted that the beginning of an active period coincides with or is located near the moment of IMF sign change. Further activity development depends on sector sign. In the first half of the year the activity level becomes high in negative sector whereas the positive IMF reduces activity. In the second half of the year the corre lation is reversed, Such dependence is in agreement with the statement that + By component of IMF produces northward (with respect to the Earth magnetic axis) com ponent during first half of the year and southward one during the second half/16,17/. The IMF sector signs distribution in 197^ according to /14/ is given at Fi g . 5« The IMP behaviour is more complicated than in previous years. In the beginning of the year the sign changes many times during a rotation but not all changes repeat at the next rotation. The positive field dominated during the first half of the rotation, the negative one - during the second half. By the end of the year the situation be comes almost opposite.negative field is typical for the first half of rotation,posi tive for th6 second half. In the first approach the field can be described as double- structured, but inside these long sectors short changes ox IMF sign can be observed. To examine the effect of IMF sign on the geomagnetic a c t i v i t y ,the average value of r^ and the daily sum of balls in Cal e n d a r ,Fig.2 for each month were selected into days w i t h positive and negative IMF (Fig.6). In April-June the mean Гц for days with negative IMF is higher than for positive days. In August-September the ratio is oppo site. Seasonal change of the character of IMF-geomagnetic activity connection is cle arly seen f r o m Fig.6b too. The estimation of activity according to the Calendar des cribes the mean duration of disturbances during the day or the number of disturbed hours. F i g . 7 shows the active day distribution versus equatorial D gt field. The IMF sign ів marked also over each row. The sequences are accompanied by D ^ variations as a rule,the magnetude of the variation gives an impression on activity in the sequence. It is seen particularly that in the beginning of the year В-sequence is placed in the positive sector is characterized by moderate disturbances. More intense disturbances are typical for С and D sequences placed in the negative sector. We must note however that the intensity of disturbances inside the sequence as well as character of sector structure changes rare during the year.