Indexed on: 08 Mar '12Published on: 08 Mar '12Published in: Geomagnetism and Aeronomy
We present a study of peculiarities of the winter nighttime maximum in the critical frequencies f0F2 at mid-latitudes of the Asian region. The data of stations located at different longitudes and close latitudes have been used in the analysis: Novosibirsk (54.8°N, 83.2°E), Irkutsk (52.5°N, 104.0°E), and Khabarovsk (48.5°N, 135.1°E). It has been found that the nighttime maximum in f0F2 is observed after midnight (∼0200–0400 LT) and is a stable feature of the quiet ionosphere from the middle of October to the middle of March at low solar activity (SA) at all analyzed stations. This interval decreases with increasing SA. The difference between the maximal and minimal f0F2 values in nighttime hours is the largest in December–January, and its amplitude is almost independent of SA. Variations in the critical frequency of the hmF2 layer are inversely related to those in the height of the maximum. We have studied periods when the difference between the daytime and nighttime values of f0F2 is less than 2 MHz. The intervals of observations of such events at different longitudes do not coincide. No dependence of the winter nighttime maximum amplitude on magnetic activity has been found.
Indexed on: 03 Apr '12
Published on: 03 Apr '12 in Geomagnetism and Aeronomy