TIME-SPACE EVOLUTION OF PEAK OCCURRENCE OF IONOSPHERIC Es IN EAST ASIA

The data observed from more than twenty stations in East Asia are compared month by month. year by year and station by station. It is found that the peak of Es occurence (place of maximal occurrence of Es)is noted for time-space evolution.Generally speaking : (1)Daytime peak is situated in low latitudes in the winter. (2)The places of daytime peak vary from low to high latitudes with the sunspot number from small to lager in the summer. (3)The peak is not clear in the equinox. (4)As for night the peak is always in about 36°N latitude. Thus it can be concluded that the peak of Es occurrence is changeable with certain regularities. This is different from the conclusions in the past.