Dependence of the Daily N m F2 Values over Mid-Latitude Stations on the Solar and Geomagnetic Activity

The results of studies of the dependence of the daily electron concentration at maximum of the F2 ionospheric layer in January 2008-2015 on the solar and geomagnetic activity are presented. The solar radio emission flux density indices F (10.7) and geomagnetic activity indices A (p) were averaged over 27 days, and aOE (c) F-10.7 >(27) and aOE (c) A (p) >(27), respectively, were obtained. Based on the data of three stations, 27-day median (with the middle of January 15) daily N (m) F2 variations were obtained for 2008-2015. Based on these data, the following paradox was discovered: in January 2014, when the values of the solar activity index F (10.7) were larger than in 2015, the dailyN (m) F2 values were smaller. Averaging over four hours of local daytime (10:00-14:00 LT) gave the daily average January aOE (c) N (m) F2 > values for each selected station for each year. To solve this paradox, a double linear regression of aOE (c) N (m) F2 > on aOE (c) F (10.7)>(27) and aOE (c) A (p) >(27) was constructed. Due to this, it was concluded that the contribution of geomagnetic activity to daily January aOE (c) N (m) F2 > values is positive. A comparison of the mean square errors of the linear and double linear regressions for aOE (c) F (10.7)>(27) and aOE (c) F (10.7)>(81) showed that the use of aOE (c) F (10.7)>(27) led to smaller errors than the use of aOE (c) F (10.7)>(81).