Ионосферные явления - 81 : материалы наблюдений Полярного геофизического института по проекту "Международные исследования магнитосферы" за 1981 г. : (оперативно-информационный материал) / Акад. наук СССР, Кол. фил. им. С. М. Кирова, Поляр. геофиз. ин-т ; [редкол.: О. И. Шумилов (отв. ред.), Л. В. Ковалевская]. - Апатиты, 1989.

5 Figure 3 presents f 0^2 va r i ations f or 1980 as well as for the previous year during quiet days. The days without magne t i c d i sturbances (rn > 15 nT) with smooth f q F 2 va r i at i o ns and without continuous distur b an c e s i n the lower ionosphere were considered quiet and are l isted in Table 1. I n w i n t e r f QF2 variation itself is ch a r acterized b y a sharp increase of m o r n i n g i o ni zation gaining the m a x i m u m n e a r n o o n w h i c h is f o ll o w ed by gradual fall towards night and m o rning hours. The n u m b e r of days t a k en f or determining the var i a ti o n s w as not large, hence the effect of d i sturbances w a s not el i minated completely. In particular, this influence is observed i n g r o wi n g of night i o n i z at i o n marked on several plots in Pig.3 . The w i d t h of the daytime m a x i m u m increases together w i t h the g r o w t h of the d u r at i o n of lu m i no s i ty periods towards summer. Da i l y f 0F2 va l u es reduce w h e r e a s night ones grow. I n s ummer time f QF2 diurnal v ar iations of quiet days pr a c ti c a ll y disappear. The increase of activity, the appearence of g e om a gnetic disturbances lead to g r ow t h of e l e c tr o n de n sity i n D a n d E layers d uring night h o u r s as well as appearence of additional ref l e ct i o ns (F-spread). The elec t ro n density is r e d uced during day ho ur s at periods a f te r p rolonged m a gn e t ic storms and intensive night time substorms. T r a n s f o rm a t io n of o r d i n ar y c o nditions and gradual g r owth of daily i o n iz a t io n last f or several days. I n s ummer time the reduce of ordinary ion i za t i on b y intensive disturbances, to some extend, restores diurnal va r i ations and d ifferences b e t w e e n day a n d night, since disturbances appear m a i n l y at night a n d are ac c o mp a n ie d b y r e d u c i n g of ionization. Several PCA events wer e observed during the year at Lo p a rs k a ya r i o m et e r plots. T o t al l y 22 p r o t o n solar events we r e detec t ed b y the s a tellites but not all gave rise to p o la r cap a b s o r p ti o n events. B es i d es a r a t h e r large amount of SCA (sudden c om m encements absorption) events we r e fo u n d at L o p a r s kaya a b s o r pt i o n plots. A m o n g the subtypes of auroral a b s o r p t i o n (AA) cases there w e r e S,F, a nd P types of AA. The R u s s i a n text presents the analysis of the i onospheric b e h a v io u r for each m o n t h of the year.