低纬电离层闪烁与总电子含量起伏的GPS观测结果

GPS Observations of Ionospheric Scintillations and TEC Fluctuations at the Region of Equatorial Anomaly

在地处电离层赤道异常区的桂林和武汉两地进行了电离层闪烁和总电子含量(QTEC)起伏的同时监测.分析和比较了两地闪烁和QTEC起伏的特征.结果表明:振幅闪烁活动主要发生在日落后至黎明,最大振幅闪烁出现率在午夜及其前后数小时,表现出对地方时的强依赖性.大部分闪烁为中等偏弱闪烁,振幅闪烁指数(S4)大小为0.2≤S4<0.3,也不时有强闪烁(S4≥0.3)发生,闪烁出现率逐日变化幅度很大,其空间分布相对集中于卫星仰角25°至50°的区域.对于大多数事件,伴随振幅闪烁活动及其强度的增强,都出现明显的QTEC的耗空和QTEC变化率(RT)的快速起伏,RT的标准差(IR)指数也明显增强,该研究说明QTEC起伏的观测可以在一定程度上预测引起闪烁的电离层不规则结构的存在.

Using the ionospheric QTEC and scintillation monitors, the QTEC and amplitude scintillation measurements of L1 （1. 575 GHz） signals from GPS satellites have been carried out at Wuhan since 2003 and Guilin since 2005. In this paper the characteristics of ionospheric scintillations and QTEC fluctuations of Wuhan are compared with that of Guilin. It is found that the amplitude scintillations mostly occur after sunset and before dawn at two sites and the highest percentage of occurrence appears near midnight,which shows strong dependence of local time. Most of amplitude scintillations is medium and weak one （0.2≤4 〈0. 3）, strong scintillations appear sometimes. Percentage of scintillation occurrence fluctuates daily. Spatially, amplitude scintillations mainly appear in the origin that elevation is between 25° and 50°. Besides, for most cases, scintillations always associate with QTEC depletion, fluctuation of RT and distinct accretion of IR. This implies that QTEC fluctuations could forecast existence of ionospheric irregularities in some extent.