Statistical Studies Of Radio Wave Amplitude And Phase Scintillation In The Ionosphere

The electron density in the ionosphere in the earth's atmosphere is not evenly distributed,and there are irregular structures of various sizes.When radio waves travel through the irregular structures in the ionosphere,they may lead to the signal fading and random fluctuation of phase,which is called ionospheric scintillation.Ionospheric scintillation is one of the most serious phenomena affecting electronic information systems.Ionospheric scintillation will reduce the performance and service quality of global navigation satellite system?GNSS?.In severe cases,signal interruption will be caused,which will result in the failure of a variety of ground to air communication systems.Therefore,scintillation research is of great significance.This paper has carried out two aspects of research:one for the amplitude scintillation of the VHF band in the polar region was statistically analyzed using the VHF band signal strength data of the three-frequency beacon reception system of the Yellow River station in the arctic from October 2011 to September 2017,and the response of amplitude scintillation to geomagnetic activities was studied;another for the phase scintillation of the L-band in the low-latitude region was statistically analyzed using GPS scintillation ground observation station receives carrier phase data of signal of dual-frequency beacon of the Nanning station in the low-latitude from 2013 to 2014,the correlation between phase scintillation and TEC fluctuation and amplitude scintillation was also investigated.The following results are obtained:?1?The amplitude scintillation in the VHF band in the polar region is very frequent,with the highest incidence of S₄ index between 0.3 and 0.4.The incidence of strong scintillation events with S₄ index greater than 0.6 is close to 70%.The seasonal distribution characteristics of amplitude scintillation in the VHF band in the polar region are not obvious.Relatively speaking,it is the highest in winter and the lowest in summer,with the spring and autumn in the middle.The local time distribution of scintillation was not obvious,and the incidence was the highest around 10 o'clock in the morning,followed by sunset.The local time distribution of scintillation incidence varies significantly with the seasons,and the strong scintillation incidence in autumn and winter is extremely around 10 o'clock in the morning and around sunset.Strong scintillation events with a S₄ index greater than 0.6 have one main minimum from after midnight to before dawn,and one sub-minimum in the afternoon.Strong scintillation incidence in summer has multiple minima in a day,especially from noon to midnight.Strong geomagnetic activity can inhibit the occurrence of strong scintillation in VHF band,but promote the occurrence of medium and weak scintillation.?2?The phase scintillation index of L1 band in the low-latitude ionosphere is the highest between 0.5 and 0.6,while the phase scintillation index of L2 band is the highest between 0.4 and 0.5.The phase scintillation index of L2 bands is lower than that of L1 bands.The phase scintillation rate in spring and autumn was higher than that in winter and summer,and showed obvious spring and autumn asymmetry.The local time distribution characteristics of phase scintillation occurrence rate are as follows:the occurrence rate of night scintillation is higher than that of day,and the scintillation activity mainly occurs from sunset to predawn,which is closely related to the formation of sunset irregulars in low-latitude areas;There is a significant linear correlation between the phase scintillation index and TEC fluctuation index,indicating that the TEC fluctuation index can effectively quantify the phase scintillation intensity,and the refraction of large scale irregular structure is the main cause of low latitude phase scintillation;there is significant linear correlation between the phase scintillation index and the amplitude scintillation index,which indicates that the amplitude scintillation and phase scintillation generally occur together,and the large scale and small scale irregular structures of low-latitude ionospheric scintillation exist at the same time;in addition,a few case studies show that there is a good correspondence between low-latitude phase scintillation index,S₄ index and TEC fluctuation index,indicating that amplitude scintillation and phase scintillation generally occur together.