中文摘要：

利用海南VHF雷达（19．5°N，109．1°E；磁纬8．1°N）在2011年7月15—22日期间的连续观测数据，对东亚低纬3m尺度电离层场向不规则体（FAI）特性进行了分析．主要结果表明，在整个观测期间，E区场向不规则体几乎每天发生，既可发生于夜间，也可发生于白天，且存在各种不同结构．根据E区场向不规则体发生的时间及形态，可将其分为三种结构类型：低部连续型结构、上部下降型结构以及白天连续型结构．这些低纬E区场向不规则体的回波谱特性与赤道电集流（EEJ）和中纬区E区场向不规则体中的2型回波相类似，但其随时间的变化与后两者存在明显差异，且与其他低纬区E区场向不规则体回波存在不同程度的差异．

英文摘要：

Using the continuous observation data of Hainan VHF radar （19.5°N, 109.1°E; dip lat- itude 8.1°N） on July 15--22, 2011, the characteristics of 3m scale Field-Aligned ionospheric Irregularities （FAI） in Eastern Asia low latitude are analyzed. The main results show the E region FAI echoes almost occur everyday during the whole observation period. They can occur both in day and night and have different complicated structures. According to their occurrence time and structure, the E region FAI echoes can be classified into the following three cases. First is the lower continu- ous echoes, which mainly occur from the later afternoon to pre-midnight （17：30 LT--23：00 LT） with evident enhanced echo intensity and negative （downward/southward） Doppler velocities. The sec- ond is the upper descend layer structures, which mainly appear from nearly midnight to pre-sunrise （23：00 LT~Oh：OO LT） with more enhanced echo intensity and both positive and negative Doppler ve- locities, where the positive Doppler velocities （upward/northward） dominate in the upper E region echoes. The third is the daytime continuous echoes, which mainly occur from morning to nearly noontime （07：00LT--11：30LT） with reduced echo intensity and both positive and negative Doppler velocities. These low latitude E region echoes mainly are type-II, which is similar to that of the Equatorial Electro jet （EEJ） and mid-latitude regions, but their temporal behavior is evidently different from that of the latter two latitudes and also has some differences with that of the other low latitudes.