Variation characteristics of sporadic-E layer in East Asia based on long-term data

The characteristics of ionospheric intensity, spatial distribution, diurnal variation, seasonal variation and long-term variation in East Asia are studied by using the ionospheric observation data from 21 ionosonde stations in China and Japan over the past 60 years. It is found that the Es layer intensity in East Asia is much higher than the global average, and the intensity center is located near the 30° N line, and weakens to low and high latitudes. At the same time, the intensity center of Es layer is not fixed, and the intensity center migrates with diurnal and seasonal variations. It is found that the regions with stronger Es showed a long-term downward trend, while the regions with weaker Es showed a long-term upward trend in East Asia.