日落后的赤道等离子体泡通过沿磁力线的电场映射，对低纬电离层E区及谷区不规则体的产生和演化具有重要作用。午夜后是赤道等离子体泡产生的另一高峰时段，然而该时段赤道等离子体泡对低纬不规则体的作用及机制尚不明确。另外，是否不同来源（本地激发和异地迁移）的赤道等离子体泡对低纬不规则体具有不同的影响？本项目利用三亚VHF雷达结合其它仪器的观测数据，统计分析在日落后和午夜后时段，低纬E区及谷区不规则体产生和演化的特征及其与赤道等离子体泡的关联；对比分析在不同来源的赤道等离子体泡作用下，低纬不规则体特征的差异。通过本项目阐明赤道等离子体泡对低纬不规则体的作用在不同时段的差异及机理；揭示不同来源的赤道等离子体泡对低纬不规则体的不同影响；明确除赤道等离子体泡外对低纬不规则体有调控作用的其它因素（如本地偶发E层、大气波动等）及可能机制。

The post-sunset equatorial plasma bubble (EPB) plays an important role in the generation and evolution of low-latitude ionospheric E (ERI) and valley region irregularities (VRI) through the electric fields mapping along magnetic field lines. However, the role of EPB during post-midnight hours and the mechanism are not clear yet. On the other hand, whether the EPBs of different origin (locally-generated and drifting-in) affect the low-latitude ionospheric irregularities in different ways. Utilizing the observations by Sanya VHF radar and other instruments, this project is devoted to analyze the characteristics of ERI and VRI and statistic their correlations with EPB during post-sunset and post-midnight hours, respectively. Compare the different characteristics of low-latitude ionospheric irregularities in the conditions of locally-generated EPB and drifting-in EPB. Through this project, the different effects of EPB to the low-latitude ERI and VRI at different time will be clarified. The different roles of locally-generated and drifting-in EPBs in the generation and evolution of low-latitude ionospheric irregularities will be revealed. In the condition that without EPB, seek other factors that modify the ERI and VRI, such as sporadic E layer (Es), local atmospheric waves and the possible mechanism will be discussed.