Statistical Characteristics of the Low-Latitude E-Region Irregularities Observed by the HCOPAR in South China

Statistical characteristics of the E-region irregularities observed by the HCOPAR in the low-latitudes of China are presented and analyzed. The data come from the observations between September 2015 and August 2016. Benefit from the high data acquisition rate and the relatively high time and height resolutions, we have found many interesting and unreported details in the statistical characteristics of the E-region irregularities. The lowest occurrence rate of the E-region irregularities appears at around sunrise and another low rate appears at around noon. The daytime irregularities are generated in the region where the zonal winds turn around at the E-region altitudes. There is clear boundary between the irregularities occurring in the morning and afternoon. The nighttime irregularities appear at higher altitudes with steeper background plasma density gradient. The higher tidal amplitude is suggested to increase the irregularity occurrence rate and the greater solar radiation is suggested to decrease it. The steep plasma density gradient in the night may be the main reason for the nighttime irregularities through gradient drift instability. The turning around of the zonal wind field is considered to generate the irregularities in the day through Kelvin-Helmholtz instability.