Physics of auroral phenomena : proceedings of the 39th annual seminar, Apatity, 29 February-4 March, 2016 / [ed. board: N. V. Semenova, A. G. Yahnin]. - Апатиты : Издательство Кольского научного центра РАН, 2016. - 167 с. : ил., табл.

median NmF2 values for diurnal variations over all 9 stations for January 19 2012, 2013, 2014 and 2015. Diurnal variations in NmF2 were obtained in terms of UT epoch and then transferred to local time (LT) diurnal variations. Daytime NmF2 anomalous dependence from solar activity in the middle and subauroral latitudes L T LT L T LT L T L T L T LT L T Figure 1. 27 day median NmF2 diurnal variation on 19 January 2012, 2013, 2014, 2015 for all considered stations. Data analysis result Figure 1 shows NmF2 27-day median diurnal variations on 19 January for four years (2012-2015) over nine stations. It is evident that the solar activity has the greatest impact on the daytimejV,„F2 values. Over all stations (exclude Port Stanley) the following paradox is revealed: the greatest daytime NmF2 values observed in January of 2015 do not correspond to the maximum in <F i0. 7>27 index (that observed on January 2014). As the following step, we calculated the 19 January daytime averaged (10:00-14:00 LT) NmF2 values (<NmF2>) for all the considered stations. On the basis of <NmF2> and <Fmrt>n values in a manner similar to ( Ratovsky and Oinats, 2011; Ratovslcy et al., 2015) we constructed the linear regressions for different data sets: (1) “without 2014” ; (2) “without 2015” ; and (3) “all years” . Linear regression coefficients for all considered datasets are shown in the Table 3. Fig. 2 shows the solar activity dependences of <NmF2> and results of all the obtained linear regressions. It is seen that: (1) the cases of “without 2015” and “all years” are close to each other and differ significantly from the case “without of 2014”; and (2) <NmF2> in 2015 has the greatest deviations from the linear regression compared to <NmF2> in other years in the “all years” case. Additionally, the linear regression in the “without 2014” case leads to negative (confusion) <NmF2> values at <F\ qj >2 t =10 that is nor seen in linear regressions for the cases of “without 2015” and “all years”. All these results demonstrate that <NmF2> on 19 January 2015 does no fit the solar activity dependence obtained for <NmF2> in other years, i.e. are anomalous from solar activity dependence view point. Analyzing Fig. 3 and Table 1, we find that the January of 2015 is characterized by the greatest geomagnetic activity compared to other years. Considering a positive deviation of <NmF2> in 2015 from the linear regression in the “all years” case, we may assume a positive impact of geomagnetic activity on the January daytime NmF2 values. Conclusions In this paper we have analyzed the solar activity dependence of the 2012-2015 NmF2 winter diurnal variations and daytime NmF2 values for different locations. We have shown that usually the daytime NmF2 depends linearly on solar activity. The following paradox was discovered: the daytime NmF2 values in January of 2014 were less than those in January of 2015, although the solar activity index <F,0.7>27 in January of 2014 was more than that in January of 2015. This paradox was seen for all the considered stations (excluding Port Stanley). 98