Research Of Ionosphere Based On Ground Based GNSS

The ionosphere is an atmospheric area in the range of 60-1000 km above the earth's surface,and is closely related to human life.Changes in the ionosphere have a great impact on navigation and positioning,radio communications,etc.Therefore,it is important to probe the earth's space and learn the physical structure and characteristics of the ionosphere by modern science and technology.GNSS has alltime,all-weather,global,and other advantages in observing the ionosphere.The content of this paper mainly includes:(1)Discussing the technological principles and methods of using GNSS to monitor the ionosphere carefully,and formulating a meaningful scheme for regional ionosphere monitoring.(2)Choosing the observation data of four monitoring stations in the Beijing area of the Crustal Movement Observation Network Of China(CMONOC)in 2014 to solve the ionospheric TEC of the puncture points.While,using three mathematical function models(polynomial function,low-order spherical harmonic function,generalized triangle series function)fitting.Separately calculating the DCB value,and comparing it with the product from the International GNSS Service center(IGS),then analyzing the accuracy of three models.(3)According to the ionospheric VTEC at the puncture points calculated by fitting models,we obtained the residual mean root mean square error of the three models.The function models are verified by comparing the ionospheric TEC derived by model fitting with GIM(Global Ionospheric Map)data provided by the Centre for Orbit Determination in Europe(CODE)of the central location of Beijing(39°56?N,116°20?E).(4)Selecting the polynomial function model,and establishing the ionosphere TEC model using the observation data from 2013 to 2017.Counting the daily mean value of the ionospheric TEC from 2013 to 2017,and analyzing the law of the variation with time and the relationship between the ionospheric TEC and solar activity.(5)Analyzing the response of ionospheric TEC to the geomagnetic storm by geomagnetic index.Finally,using BP neural network model to predict ionospheric TEC.Experiments show that the fitting accuracy of the three function models in Beijing is equivalent,and the accuracy of the polynomial function model is slightly higher than that of other models.The TEC value of the ionosphere is highly correlated with solar activity,which is significantly higher in the solar high year than the solar low year.The ionospheric TEC shows the characteristics of annual change and seasonal change.The ionospheric TEC response to the geomagnetic storm is reflected in the change of geomagnetic index.In the ionospheric prediction,the more input parameters,the higher accuracy.