The Research And Analysis Of Ionosphere Two/Three-Dimensional Data Assimilation Modeling

Ionosphere is an important part of the earth's upper atmosphere.It closely related to radio wave as ionosphere contains a lot of free electronics.Total Electron Content?TEC?is proportional to the time-delay error of satellite signals'passage through ionosphere.Therefore,it has important value for modeling of ionosphere.In this paper,data assimilation,which have been widely used in the atmospheric sciences and ocean sciences,was used to build the ionosphere model.Based on the actual observations of the ionosphere,2D/3D data assimilation models were developed on empirical models or theoretical models to make the grid parameters of ionospheric which are closer to the real observations.The main contents and results are presented as follows:?1?Kalman filter method was used to develop reginal and global 2-dimensional data assimilation models of the ionosphere based on different background modles and different kinds of observation data.The influence of data assimilation on different background models was further analyzed.Modeling and analysis can show the effectiveness of the data assimilation model in the ionospheric model.Observations with uneven distribution of grid correctted the background model with uniform grid,and corrected the grids without observations.The TEC verification in 2015 showed that the TEC standard deviation?SD?is lower than 6TECU in daytime and lower than3TECU in nighttime.The f_oF₂ SD in 2015 is lower than 2MHz.?2?TEC from ionosphere data assimilation model in China was analyzed and compared with other ionosphere products.The results showed that GIM-TEC has a similar distribution to the data from assimilation model,but there are some differences in low latitudes of China.The comparison of different TEC median showed that the GIM-TECs are mostly larger than assimilater TEC,while they are sometime smaller than assimilater TEC after noon at low latitude.The assimilated TEC was then used to analyze the ionospheric response to geomagnetic storm in the four seasons of 2015,which suggested the different mechanism during different geomagnetic storms.The disturbed electric field and neutral wind can induce ionospheric positive response,whereas neutral composition and disturbed electric field is responsible for the long-term negative storm.?3?A 3-dimensional ionosphere electron density data assimilation model with multi-source observation was developed.Different types of data have different effects on data assimilation results.For electron density at one point,it contains the least information and has a limited range of influence on the global scale.For line type data,-like TEC,it contains information about all electron densities in the integration path and has a large range of influence.The biggest advantage of the 3-dimensional data assimilation model is that it can give the electron density profile.Because the calculation the 3-dimensional data assimilation model need large machine resources,it is suggested to use regional data assimilation to analyze details of the electron density profile.