Study on Observations of Daytime Spread-F-Like Irregularity in Mid-Latitude Region

Based on the HF Doppler frequency shift observation, daytime spread-F-like phenomenon occurred at mid-latitude region and the relationship between the daytime spread-F-like and other ionospheric disturbance are studied. The results show that the daytime spread-F-like phenomena have the characteristics of large range of occurrence time, long duration time and are accompanied with other ionospheric disturbances. The morphological features are the blurred echo traces which are similar to those of the nighttime spread-F, frequency shifts of these echoes tend to be positive, and sometimes are accompanied by Traveling Ionospheric Disturbances (TIDs). Although the daytime spread echoes phenomenon occasionally occur and the occurrence rate is very low, the temporal and spatial broad distribution of the daytime spread-F-like implies that its effect on the space weather cannot be ignored, and its properties can not be replaced simply by that of spread-F usually occurred at nighttime. Therefore, the study of the daytime spread-F-like has very important significance.