Investigations of Ionospheric E-region Field-aligned Irregularities Observed with Kunming VHF Radar

The statistical characteristics of mid-low latitude ionospheric E-region field-aligned irregularities (FAI) observed with the Kunming very high-frequency (VHF) radar are presented. First, the observational results show that the irregularities appeared mainly in periods before noon and near night, with the nighttime echoes being more intense and covering a greater height extent than that during the daytime. Second, we observed the existence of two well-defined types of echoes in the nighttime: the lower E-region echoes (115-130km) and upper E-region echoes (130-150km). Moreover, there are differences in FAI's motion characteristics at different range in the daytime and nighttime. Without in-field measurements, it is difficult to verify what physical mechanisms may explain the formation of the irregularities, which we will combine other facilities to analyze it in the future.