In this study, the association of Equatorial Ionization Anomaly (EIA) with various post sunset ionospheric irregularity manifestations are brought out empirically using Global Positioning System derived Total Electron Content (GPS - TEC) data from five stations centered around 77° E longitude as well as ionosonde data at a dip equatorial station Trivandrum (geographic latitude 8.5° N ; geographic longitude 77° E) for the days of vernal equinox season of distinct solar activity conditions. The study reveals that the EIA crest magnitude in the evening hours has a direct control on the base height of post sunset ionospheric F- layer (the primary factor responsible for the generation of ionospheric plasma irregularities) on a day-to-day level. Under the condition of strong (weak) EIA crest, the equatorial spread F irregularities are observed to be manifested earlier (later) and are sustained for a longer (shorter) duration. Further, the GPS signal scintillation intensity (quantified by the parameter S4 index) exhibits a direct association with EIA crest strength. This work emphasizes the need to incorporate various EIA features in the current models for better prediction of post sunset ionospheric plasma irregularities which are known to be hazardous for communication and navigation systems.

在这项研究中，赤道电离异常 (EIA) 与各种日落后电离层不规则表现的关联是使用全球定位系统得出的总电子含量 (GPS - TEC) 数据从以东经 77° 为中心的五个站以及特里凡得琅倾角赤道站（地理纬度 8.5° N；地理经度 77° E）的电离探空仪数据，用于不同太阳活动条件的春分季节天数。研究表明，傍晚时分的 EIA 波峰震级在日常水平上直接控制了日落后电离层 F 层（导致电离层等离子体不规则产生的主要因素）的基础高度。在强（弱）EIA波峰条件下，观察到赤道传播 F 不规则性较早（较晚）出现并持续较长（较短）的持续时间。此外，GPS 信号闪烁强度（由参数 S4 指数量化）表现出与 EIA 波峰强度的直接关联。这项工作强调需要在当前模型中加入各种 EIA 特征，以便更好地预测日落后电离层等离子体不规则性，这些不规则性已知对通信和导航系统是危险的。