Diurnal, seasonal, annual, and semi-annual variations of ionospheric parameters at different latitudes in East Asian sector during ascending phase of solar activity

We analyzed ionospheric parameters including the critical frequency of the F2 layer (foF2), the peak height of the F2 layer (hmF2), and the scale height at hmF2 (HT) from 2006 to 2012 (ascending phase of solar activity) at Hainan (19.5° N, 109.1° E, MLat. 9.7° N), Irkutsk (52.4° N, 104.3° E, MLat. 42.5° N), and Norilsk (69.2° N, 88.0° E, MLat. 59.8° N) stations (low, middle and high latitudes). We have used manual scaled digisonde ionogram data. Studies of foF2 and hmF2 diurnal-seasonal variations continue those made earlier for East Asia. Features peculiar for the ascending phase of solar activity are mostly consistent to those for descending phase, except for the features of sunset and nighttime hmF2 variations. Features of annual and semi-annual variations recorded by a digisonde agree with those obtained by a satellite occultation and TEC map. We also obtained seasonal, diurnal, annual, and semi-annual variations of the ionospheric parameter HT (scale height at hmF2) from digisonde data, which differ from foF2 variations and hmF2 features.