Ionospheric Modeling And Application Based On GNSS

The ionosphere is an important part of the Sun-earth space environment,and its variation is closely related to solar activities.The ionosphere has a significant impact on navigation and positioning,aerospace,communication and space weather prediction and early warning.Therefore,it is of great significance to explore the structure of the ionosphere and build a high-precision ionosphere model.At present,the Global Navigation Satellite System(GNSS)has become the most effective means of ionospheric detection.This paper carries out ionospheric modeling based on GNSS data,and analyzes the spatio-temporal variation characteristics of the ionosphere based on the constructed ionospheric model.Its main research work is as follows:A new inversion method for ionization chromatography is proposed in order to solve the problem of misalignment in ionization chromatography and the dependence of electron density on the initial value given by the background model in pixels that are not traversed by rays.In this method,Empirical Orthogonal Function(EOF)is adopted in vertical direction to transform the original problems and reduce the number of conditions in the equation.The smooth constraint is applied in the horizontal direction and then the algebraic reconstruction algorithm is used to solve the problem.The reconstructed results show that the inversion results of the new algorithm are consistent with the simulated electron density.In order to verify the effect of the new algorithm on ionospheric disturbance,the 3D ionospheric electron density distribution in the European region is reconstructed by the new scheme.The reconstructed peak density and peak height of the ionospheric are in good agreement with the observation results of the altimeter,indicating that the new algorithm has a good effect on the reconstruction of the spatio-temporal distribution of ionospheric electron density during the magnetic storm.With the development of multiple navigation satellite systems,multi-system integration modeling has become the trend of ionospheric modeling.In this paper,Differential code bias(DCB)of satellites and receivers is estimated by combining BDS3 and GAILEO system into the global ionospheric modeling.In order to improve the accuracy of the ionospheric model of ocean region,differential code data of ocean altimeter is introduced.The results show that after the addition of GAILEO and BDS3 systems,the number and distribution range of satellite puncture points have been significantly improved,thus improving the accuracy of the ionospheric model on land and ocean regions,especially in ocean regions.The calculation results of GAILEO and the satellite DCB of BDS3 are in good agreement with the official product release.In response to a magnetic storm event in November 2021,in this paper,the Global Ionospheric Model(GIM)provided by the Center for Orbit Determination in Europe(CODE)will be applied to monitor the ionospheric electron content(TEC)Change over Europe.In order to analyze the ionospheric irregular disturbances during magnetic storms,GNSS data in the European region were used to calculate the Rate of TEC Index(ROTI).In order to monitor the changes in the vertical structure of the ionosphere and analyze the physical mechanism of ionospheric disturbances,Local altimeter data and O/N2 data are used.The results show that the ionospheric changes in the European region during magnetic storms are complicated.A large number of ionospheric irregularity appears in the high latitude region,and the peak height of the ionospheric layer increases significantly during magnetic storms,which is caused by the interaction of O/N2 components and the east-penetrating electric field.