Low-Latitude Ionospheric Scintillation Monitoring And Prediction Based On In-Situ Satellite Observations

When a radio wave signal passes through electron density irregularities,the phase,intensity and polarization of the radio wave signal change irregularly,that is,ionospheric scintillation.Ionospheric scintillation seriously threatens the performance of radio systems such as satellite communications,navigation and positioning,and radar monitoring.The Global Navigation Satellite System(GNSS)is widely used in social production and life,and people's reliance on GNSS is increasing.Therefore,GNSS ionospheric scintillation prediction has become a hot topic in space weather research.GNSS ionospheric scintillation is frequent in low latitude regions,and the characteristics of day-to-day variation are very significant.Monitoring GNSS ionospheric scintillation in low latitude and exploring the method of ionospheric scintillation prediction will help to promote the research of ionospheric scintillation prediction and reduce the threat of ionospheric scintillation to the performance of radio systems.Sanya(geographic coordinates: 18.3°N,109.6°E;geomagnetic latitude: 8.27°N)and Guilin(geographic coordinates: 25.29°N,110.33°E;geomagnetic latitude: 15.04°N)are located in the low-latitude regions,where ionospheric scintillation occurs frequently and the impacts of ionospheric scintillation are significant.In this paper,the Communications/Navigation Outage Forecasting System(C/NOFS)satellite in-situ observations and GNSS ionospheric scintillation data recorded at Sanya and Guilin and global Vertical Total Electron Content(VETC)data during the high years of solar activity(i.e.,October 2011 and 2012 to 2015)were used to carry out the following work.1.The analysis and processing program of C/NOFS satellite in-situ observations data was developed,and the correctness of the program was verified.2.The influence of the ionospheric F-layer plasma vertical drift velocity over the magnetic equator during the sunset on the day-to-day variation of GNSS ionospheric scintillation in low latitudes was analyzed based on the C/NOFS satellite in-situ observations of ion drift velocity data and GNSS ionospheric scintillation data of low latitude regions(i.e.,Sanya and Guilin).The analysis results show that compared with the non-scintillation day,the ionospheric F-layer plasma vertical drift velocity over the magnetic equator during the sunset in scintillation day was greater,and even several times.That is,the pre-reversal enhancement(PRE)of the ionospheric F-layer electric field over the magnetic equator during the sunset on scintillation day was stronger.3.Since the ionospheric F-layer plasma vertical drift velocity over the magnetic equator during the sunset has an important influence on the distribution of electron density along latitudes after sunset,in this paper the characteristics of the variety of geographic longitude 110°E VTEC with latitude after sunset in scintillation days and non-scintillation days of Sanya and Guilin(the geographic longitude of the two places is about 110oE)were investigated utilizing GNSS ionospheric scintillation data recorded at Sanya and Guilin and global VETC data to verify the effects of the ionospheric F-layer plasma vertical drift velocity over the magnetic equator during the sunset on the day-to-day variation of GNSS ionospheric scintillation in low latitudes.The results show that the ionospheric F-layer plasma vertical drift velocity over the magnetic equator during the sunset was the largest when scintillation occurred in both Sanya and Guilin,followed by when scintillation occurred in Sanya and no scintillation occurred in Guilin,and the smallest when no scintillation occurred in Sanya and Guilin.4.To explore the feasibility of the method using the plasma irregularities in-situ observed by satellites in the ionospheric F-layer over the magnetic equatorial ionosphere to predict the occurrence of GNSS ionospheric scintillation in low latitude regions,the C/NOFS satellite in-situ observations of ion density data and GNSS ionospheric scintillation data of low latitude regions(i.e.,Sanya and Guilin)were analyzed.The results show that for the Sanya GNSS ionospheric scintillation that occurred from sunset to sunrise of the next day,the prediction success rate of this method was 67.03%.For the Sanya GNSS ionospheric scintillation that occurred from sunset to midnight,the prediction success rate of this method was 81.22%.For the Guilin GNSS ionospheric scintillation that occured from sunset to sunrise of the next day,the prediction success rate of this method was 29.03%.For the Guilin GNSS ionospheric scintillation that occurred from sunset to midnight,the prediction success rate of this method was 34.27%.The results show that the method using the plasma irregularities in-situ observed by satellites in the ionospheric F-layer over the magnetic equatorial ionosphere to predict the occurrence of GNSS ionospheric scintillation in low latitude regions was only applicable to lower latitudes(namely Sanya),and the prediction success rate of GNSS ionospheric scintillation that occurred from sunset to midnight was higher than the prediction success rate of GNSS ionospheric scintillation that occured from sunset to sunrise of the next day.