An intense Storm Enhancement Density (SED) event with the magnetic storm occurred on 17–24 March 2015 has been investigated. The morphological character of the SED during different phase of the magnetic storm is examined and compared with the non-storm time. Three intensity indexes, i.e., “general” SED index, “heavy” SED index and “severe” SED index, are defined to represent the intensity of SED respectively represented by the numbers of the ionospheric total electron content (TEC) grids with TEC > 60 TECu, TEC > 80 TECu and TEC > 100 TECu. The temporal evolution of the SED intensity indexes during a time span covering the non-storm time and the magnetic storm time have also been investigated. The SED exhibits a shape with two parallel slender troughs in the middle and low latitudes during the non-storm time and then gradually develops into an ellipse structure as the development of magnetic storm. The intensity of SED and the fluctuation of the TEC evolution are generally corresponding to the fluctuation of Dst index. The analyzing results enrich our understanding of the temporal and spatial evolution of the ionospheric SED.

研究人员调查了2015年3月17日至24日发生的与磁暴有关的强烈风暴增强密度（SED）事件。检查了SED在磁暴不同阶段的形态特征，并将其与非暴风雨时间进行了比较。定义了三个强度指标，即“一般” SED指标，“重” SED指标和“严重” SED指标，分别代表电离层总电子含量（TEC）栅格数表示的SED强度，TEC> 60 TECu，TEC> 80 TECu和TEC> 100 TECu。还研究了覆盖非暴风雨时间和磁暴时间的时间跨度中SED强度指数的时间演变。在非暴风雨期间，SED在中低纬度呈现出两个平行的细长槽的形状，然后随着磁暴的发展逐渐发展成椭圆形。SED的强度和TEC演化的波动通常与Dst指数的波动相对应。分析结果丰富了我们对电离层SED时空演变的理解。