Peculiarities of the night-time winter increase in the critical frequency of F2 layer over Irkutsk
Abstract
We present an analysis of peculiarities of the night-time winter foF2 increase (NWI) in the East Siberia. Data from ionospheric station Irkutsk (52.5 N. 104.0 E) in the periods 1958-1992, 2002-2010 and the empirical model of the F2 layer critical frequency under magnetically quiet conditions deduced from these data (model Q-F2) are used in this study. Based on the model Q-F2, we revealed the NWI to be the stable regularity of quiet ionosphere over Irkutsk in the interval from the middle of October to the middle of March under the low solar activity. This interval decreases as the solar activity increases. The amplitude of the NWI (the difference between maximum and minimum values foF2 in the night hours) is maximum in December-January and nearly constant in the transition from the low to middle solar activity. Maximum in night foF2 in the quiet geomagnetic condition is observed mainly after midnight ( 02-04 LT) but is shifted to the subsequent hours as the solar activity increases. Day to day variability in foF2 in this maximum is rather strong and the changes in foF2 are often opposite to the changes in the hmF2. There are presented the examples of the strong night-time foF2 increases. The most pronounced event is the night-time enhancement of foF2 on 19 December, 2008 to the values typical to the day-time maximum of foF2 in that and adjacent days. These extreme cases are rare in occurrence. Nevertheless, the analysis showed that the strong foF2 increases are more often observed in December-January under the low solar activity during the minor magnetospheric substorms, other than storms. It is given a qualitative interpretation of listed properties of NWI over Irkutsk.
- Publication:
-
38th COSPAR Scientific Assembly
- Pub Date:
- 2010
- Bibcode:
- 2010cosp...38.1055P