Measurements with DPS-4 digisonde at Hainan station(19.5oN,109.1oE)covering a solar cycle(2002-2012)during quiet time are analyzed to explore ionospheric temporal variations in low latitude region.Diurnal,seasonal,and solar activity variations of the ionospheric peak parameters(foF2,hmF2,and Chapman scale Height Hm)are studied.The results show that the winter anomaly in the daytime foF2 appears in different phases of solar activity and its duration increases as solar activity increasing.
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