中纬地区日间类扩展F不规则结构的观测研究

基于高频多普勒观测，研究中纬地区日间类扩展F现象及其与其他电离层扰动现象的关联.结果表明:日间类扩展F具有出现时间覆盖面广、持续时间长、与其他电离层扰动相互伴随等特征；形态特征表现为回波弥散（与夜间扩展F相似），弥散回波的频移多倾向于正向偏移，有时与行进电离层扰动（TIDs）相互伴随.日间类扩展F现象虽然是偶发事件，且发生率极低，但其出现时间及区域的广泛性充分体现了该现象对空间天气及空间环境的影响具有不可忽视的重要性. 

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.