The spread F data obtained over Lanzhou (36.1°N, 103.9°E), Chongqing (29.5°N, 106.4°E) and Haikou (20.0°N, 110.3°E) of China during the period from 1978 to 1997 are used to analyze the occurrence characteristics. The statistical results show that the post midnight spread F occurrence is maximum during the summer solstice months of the lower solar activity period, while post sunset spread F is dominant in equinoxes of higher solar activity period over Haikou station. Over Chongqing and Lanzhou stations, spread F mostly occurs at post midnight and relates negatively with solar activity. Using regression method and Fourier expansion, the preliminary single-station model of spread F occurrence is established and the accuracy of the model is evaluated.
spread F, solar cycle variation, seasonal variation, empirical model
Citation:Xu T, Wu Z S, Hu Y L, et al. Statistical analysis and model of spread