中文摘要：

电波穿越电离层时，由于受到电离层不均匀结构的影响，电波的幅度、相位、时延等有时会发生快速抖动，这就是所谓的电磁波电离层闪烁现象．电离层闪烁会影响卫星通信系统的质量和导航系统的精度．本文分析了GPS信号研究电离层闪烁的基本原理，讨论了电离层闪烁监测中S4指数的计算方法及其修正方法．通过数据模拟，评估了原始S4指数计算方法及其修正方法的性能特点．针对原始S4指数计算方法及修正方法的不足，提出了一种新的修正方法，并采用实测GPS数据对上述方法进行了检验．结果表明，上述方法是有效的和可靠的．

英文摘要：

Ionospheric scintillations are rapid variations in the amplitude and phase of radio signals resulting from density irregularities in the ionosphere. Ionospheric scintillations influence adversely the performance of satellite communication system and the precision of navigation system. In this paper, the traditional computational method of ionospheric S4 index based on GPS signal is analyzed. In view of the insufficiency of the primitive $4 index computational method and the correction method, a new correction method is proposed. In order to test these methods, further study which is based on data from GPS receivers has been made. The result indicates that the primitive S4 index computational method and the correction method are feasible and reliable.