磁暴期间全球TEC扰动特性分析

磁暴期间白天电离层总电子含量（TEC）大幅度扰动.TEC扰动与磁暴发生时的世界时（UT）有关.利用7年的数据对TEC对磁暴的响应进行统计研究.结果显示，磁暴期间白天TEC增大明显，且在午后TEC的增大比例有一个高峰.在18:00UT-04:00UT，南美地区与其他地区相比TEC增长较大，这可能与白天的光照有关.为了研究TEC变化与磁暴的关系，结合同样时间段的Dst指数，把TEC数据分为磁暴日（Dst<-100nT）和平静日（Dst>-50nT）.研究发现，将TEC前移2h，低纬日侧地区TEC增大值随着世界时的变化与Dst变化的负相关性较好，相关系数为-0.75.在中纬度地区，将TEC扰动前移1h，相关系数为-0.61.这可能是行进式大气扰动携带着赤道向的子午风，由极区向低纬传播引起.可以认为，TEC的变化可能是由磁暴引起的.在高纬地区，TEC增大值随着世界时的变化与Dst变化的相关性较差.这可能是由于太阳高度角较低，光辐射通量较小，导致电子密度的增加不明显. 

Statistical Study on the Response of TEC to Geomagnetic Stormsormalsize

The ionospheric Total Electron Content (TEC) in the daytime is often greatly disturbed during geomagnetic storms. Recent reports suggest that the disturbance of TEC depends on the Universal Time (UT) of storm onset. By using the TEC global maps over a 7-year period produced by the Jet Propulsion Laboratory, the response of TEC to geomagnetic storms is investigated. The analysis confirms that TEC increases obviously in day time, and extends across the noon sector with an afternoon peak. In 18:00UT-04:00 UT, American sector continues to exhibit a storm time, which TEC enhancement is higher than those observed in the other sector. It is possibly related to the sunlight in day time. In order to study the relation between TEC enhancement and the corresponding magnetic storms, the TEC data are divided into quiet (Dst>-50nT) and active (Dst<-100nT) sets using Dst index. The results show that the TEC variation at low latitudes has negative relation to Dst as the TEC variation is moved forward about 2 hours. The relation coefficient is -0.75. The TEC variation at middle latitudes has negative relation to Dst with a coefficient of -0.61, as it is moved forward about 1 hour. The reason may be that the travelling atmosphere disturbance carries the equatorial meridional wind, and propagates from polar region to low latitude. It can be concluded that the TEC variation is induced by geomagnetic storms. However, the correlation is poor at high latitudes. It is possibly because of the complexity of sectors at high latitudes.