Study Of Ionospheric Tec Gradient Anomaly Detection Based On GPS Data

The total electron content(TEC)gradient characteristics of the ionosphere have been an important topic in ionospheric research for many years.A TEC gradient anomaly detection method based on multi-resolution tomography is introduced,which verifies the effectiveness of multi-resolution tomography in the magnetic storm period and magnetic quiet period,according to the range and cause of the TEC gradient,the gradient characteristics of the ionospheric TEC are studied from different aspects in this study.Firstly,in order to effectively detect the ionospheric structure,a multi-resolution ionospheric tomography technique based on GPS data is introduced,and compares the results of single-resolution tomography and ionosonde to analyze the accuracy of the method during the magnetic storm period and magnetic quiet period.The results show that the accuracy of multi-resolution tomography is higher than single resolution in both the magnetic quiet period and the magnetic storm period,and it can accurately reflect the ionospheric electron density distribution.Secondly,the TEC gradient of the ionosphere is studied by the multi-resolution tomography.The research shows that during the magnetic quiet period,the TEC gradient in the low latitudes shows the strongest gradient change in the selected four seasons,and most of them are north-south gradients.The TEC gradient in the mid-latitudes is slightly smaller,but irregular local TEC gradients begin to appear.There are few large-scale TEC gradient in high latitudes,but local irregular TEC gradients are the most;When studying the small-scale TEC gradient during the magnetic storm and magnetic quiet period,by introducing the ?TEC variable,it is analyzed that the magnetic storm has a great influence on the small-scale TEC gradient,and the TEC gradient is discussed from different directions.When studying the TEC gradient anomaly characteristics between two stations in eastern China,the ionospheric gradient value in Hong Kong is calculated to be up to 48.03mm/km based on the observation data of GPS No.28 satellite,and the influence of TEC gradient anomaly on GBAS is discussed.Finally,since ionospheric disturbance is one of the main causes of TEC gradient anomaly,the TEC gradient anomaly induced by large-scale travelling ionospheric disturbances(LSTID)is studied.The results show that large-scale ionospheric disturbances occurred during the magnetic storm period,with two stages.The first stage of the LSTID has a wavelength of about 1200 km and a period of 50-60 min,which propagates southwest at a wave speed of 350-400 m/s.In the second stage,the “super” LSTID appeared,covering a large area and a long wavelength.The vertical electron density information of the ionosphere was analyzed,and the cause of LSTID was evaluated.When analyzing the TEC reconstruction map,the ionospheric large-scale TEC anomaly gradient in the corresponding region during LSTID is obvious,and the larger the LSTID amplitude,the more significant the influence on the TEC gradient.