Modeling And Analysis Of Ionospheric TEC In China

The ionosphere is the most important area for human space activities,and the Total Electron Content(TEC),which describes the structure,state and change of the ionosphere,has always been one of the key parameters of space physics and geodesy.How to construct an accurate ionospheric TEC model is one of the hotspots in the field of Global Navigation Satellite Systems(GNSS)and the ionosphere.This paper is based on the TEC data of the Center for Orbit Determination in Europe(CODE),the GNSS observation data of the Crustal Movement Observation Network of China(CMONOC)and the Massachusetts Institute of Technology(MIT)TEC data released by Haystack Observatory,using two methods of Empirical Orthogonal Function(EOF)and spherical harmonic function to construct ionospheric TEC maps in China,and compare the effectiveness of different methods in constructing ionospheric TEC maps in China sex and practicality.The main work of this paper is as follows:1)Using the EOF method to analyze CODE-TEC data in China from 1998 to2010,the analysis results show that the average value of CODE-TEC in China from1998 to 2010 and the time-space distribution of the first-order basis function after EOF decomposition The characteristics are consistent,which mainly reflect the latitude and diurnal variation characteristics of TEC in China.The first 4-order EOF components accounted for 90.3813%,3.4580%,1.1965% and 0.7834% of the total variation of ionospheric TEC in China.The amplitudes of the first four-order EOF component coefficients after EOF decomposition all have obvious semi-annual or annual changes,which are modulated by the solar activity index F10.7 and the first-order coefficients have an obvious period of about 11.00 years.2)Using the real-time GNSS observation data of CMONOC,fitting the real-time coefficient of the EOF component,constructing the real-time ionospheric TEC map in China,and comparing it with the vertical TEC map at the ionospheric penetration point in China,CODE-TEC and the solar activity index F10.7 The real-time ionospheric TEC map of China(F107-CIM)constructed by driving is compared and analyzed,and the results show that the real-time ionospheric TEC map constructed by EOF and the vertical TEC at the ionospheric penetration point in China are in time and space.The distribution has good consistency.In the high solar activity year(2014),the absolute error between the two is mainly distributed between-5.00～5.00TECU;in the low solar activity year(2016),the absolute error between the two is mainly distributed between-3.50～3.50 TECU.The real-time ionospheric TEC map constructed by EOF in China is more consistent with the CODE-TEC ionospheric TEC map in China in terms of time and space distribution,and there is an obvious difference with F107-CIM.F107-CIM is generally larger than that constructed by EOF in China Regional real-time ionospheric TEC maps and CODE-TEC.Constructing a real-time ionospheric TEC map in China through EOF and CODE-TEC in the years of high solar activity,the mean root mean error of the absolute error is mainly distributed around 8.03 TECU;in the low solar activity year,the mean root mean error of the absolute error The main distribution is about 4.49 TECU.Therefore,the ionospheric TEC model in China constructed by using the EOF method combined with real-time GNSS observation data can quickly give the real-time distribution of ionospheric TEC in China.The distribution has good consistency.3)Based on the vertical TEC and MIT-TEC data at the ionospheric penetration point in China,the Chinese ionospheric TEC is constructed using spherical harmonics.The research results show that the error of the ionospheric TEC model in China constructed with the 15 th order spherical harmonic function is small;the model can not only reflect the variation characteristics of TEC in China with time and latitude,but also clearly show the equatorial anomalous area of ionospheric TEC.latitude range.Overcome the uneven distribution of vertical TEC and MIT-TEC data in different regions at the ionospheric penetration point in China,give full play to the advantages of various TEC observation data,improve the spatial coverage of ionospheric TEC,and effectively improve regional Accuracy of the ionospheric TEC model.The comprehensive comparative analysis shows that: using the EOF method combined with the vertical TEC at the ionospheric penetration point in China can quickly construct the ionospheric TEC in China,and the model accuracy is slightly lower than using the spherical harmonic function to construct the vertical TEC at the ionospheric penetration point in China.The calculation speed of the Chinese ionospheric TEC map constructed from the TEC and MIT-TEC data is lower than that of the EOF method.The research on the construction methods of different ionospheric TEC models in China is of great significance in the aspects of the ionospheric response to space weather events and the correction of radio wave propagation errors.