Ионосферные явления-78: материалы наблюдений Поляр. геофиз. ин-та по проекту Междунар. исслед. магнитосферы за 1978г. (оперативно-информационный материал). Апатиты, 1979.

5 The K A itself is not accompanied as a rule by magnetic disturbances,but intense mag­ netic storm often follows КЗА» PGA events were registered in February,May and Septem ber. The increasing of absorption in day and evening hours were registered between 13 and 15 February, Days were moderately disturbed,but the absorption variation was not correlated with magnetic disturbances. In the last day a relatively short disturbance with unusually intense positive bay arise near noon hours. A more intense event hap­ pens between 29 April and 3 May» The absorption increasing began on 28.IX at magne­ tically calm day. High values of absorption were registered in day hours of the fol­ lowing days and gained maximum on 3 0 »IY. The absorption reduces each time by nignt and grows again at noon hours of the next day. BOA event was followed by the most se­ vere magnetic storm of 1978,with Sc at 09.52 ОТ 3 0 .IY. Additional increasing of ab­ sorption similar to PGA is registered during one day - 7.x. The last PGA event is re­ gistered between 23 and 25»DC. Smooth absorption increasing at moderately disturbed magnetic field arises in evening hours of 2 3 .IX. High values were registered during the following days. The absorption increased at diffei'ent h o u r s 9 but decreased each time at late evening. The appearance of magnetic disturbances during these days were not correlated with the change of absorption. PDA was followed by severe magnetic storm, which intensity was leas only the storm after FCA in May. E and FI layers during winter months are not seen} at spring critical frequen­ cies and duration of their registration increased. At summer season the layers are observed continuously, the diurnal variation of FI layer displayed weaker than El- layer variation. The character of diurnal variation of electron density at F2 level can be obtained from median values of foF2 on quiet days,presented at Fig.2. As quiet were choosed the days without magnetic disturbances (r^ < l5nT),with smooth £oF2 va­ riation and without long disturbances in the lower ionosphere. The list of these days is given at Table 4. The median values are determined for every pair of the months exept summer season. It is seen that the increasing of sunspot numbers leads to exce­ eding of foF2 values in the second half of the year comparing to the same season in the first half of the year and the exceeding of values in this year with compare to the corresponding season of the previous year. The foF2 variation in winter season can be described as sharp increase up to high values during short period of ionosphere illumination. The increasing in morning hours seems to be faster than the decreasing in afternoon hours. At night hours foF2 is small and the character of its variation is not the заде at different graphs. The night time median values ere connected with disturbances,which effect is not fully excluded. From the given f-plot it is seen that during many nights the electron den­ sity decreases below the ioa: londe threshold. At equinox months the duration of peri­ od with high values of electron density increased, in summer the ionosphere is illu­ minated continuously and the diurnal variation reduces. The noon value of foF2 in summer is lower than in winter and equinox. The disturbances in winter sяaeon lead to increasing of nighttime electron den­ sity at all levels of ionosphere. It manifests in fmin increasing, in occurence of dence sporadic E-layer,the increasing of fo?2 and the appearance of the additional reflecting regions at F2 level. The presence of disturbances give the diurnal varia­ tion of foF2 in winter season the shape of double wave with maxima near noon and mid­ night and minima at evening and morning hours. At noon hours at all seasons the dis­ turbances reduces foF2. From f-plots it is seen that the parts of disturbed period, where the absorption is not very high,foF2 is reduced. During the period of recovery after ionosphere disturbances foF2 also reduced. The diurnal, variation at winter and equinox seasons is assymmetric. Ifee electron density in afternoon hours decreases