极区电离层VHF波段振幅闪烁发生率的统计研究

Statistical Studies on the Occurrence Rate of VHF Amplitude Scintillation in the Polar Ionosphere

电离层闪烁会引起地空无线电系统的信号幅度、相位的随机起伏,使系统性能下降,严重时可造成通信系统、卫星导航系统、地空目标监测系统信号中断.该文利用位于挪威斯瓦尔巴岛黄河站的三频信标接收系统的VHF波段信号强度数据,对2011年10月至2017年9月期间极区电离层VHF电波振幅闪烁强度和出现率的季节和地方时分布特征及其对地磁活动的依赖性进行了统计分析.结果表明:极区VHF波段的振幅闪烁发生率很高,且以强闪烁活动为主,S4指数大于0.6的发生率接近70%;振幅闪烁的季节分布特征表现为冬季发生率最高,夏季最低,春秋居中;闪烁发生率的地方时分布随季节变化差异显著,秋冬季的强闪烁发生率极大出现在上午10点前后和日落前后,从午夜后到黎明前有1个主极小,午后有1个次极小,夏季强闪烁发生率在一天中出现多个极小,从正午到午夜的几个极小尤为显著;强地磁活动对VHF波段强闪烁的发生有抑制作用,而对中等强度和弱闪烁的发生有一定的促进作用.

Ionospheric scintillation can cause random fluctuation of signal amplitude and phase of the ground-to-air radio system, degrading the system performance, and it may cause signal interruption of the communication system, satellite navigation system and ground-to-air target monitoring system in some serious cases. Based on the VHF signal intensity data from the tri-band beacon receiving system at Yellow River station’s located in Svalbard, Norway, the occurrence rate of VHF wave amplitude scintillation intensity and its seasonal and local time distribution characteristics in the polar ionosphere between October 2011 and September 2017 were statistically analyzed, and the dependence of wave amplitude scintillation on geomagnetic activity was statistically analyzed. The results show that there is a high occurrence rate of VHF amplitude scintillation in the polar region which mainly shows strong scintillation events, the incidence rate of S 4 index greater than 0.6 is close to 70%. The seasonal distribution of amplitude scintillation is characterized by the highest occurrence rate in winter, the lowest in summer and the middle in spring and autumn. The local time distribution of scintillation occurrence rate varies significantly with season. The maximum occurrence rate of strong scintillation in autumn and winter is around 10:00 LT and sunset, and there is a major minimum from post-midnight to pre-dawn sector, and a sub minimum in the postnoon. In summer, there are many minima of the occurrence rate in a day, several minima from noon to midnight are particularly significant. Strong geomagnetic activity has an inhibitory effect on the occurrence of strong scintillation in the VHF band, but promotes the occurrence of moderate and weak scintillation to some extent.