Ionogram Inversion Research For Wuhan Ionospheric Sounding System

The Wuhan Ionospheric Sounding System (WISS) is a Multifunctional ionospheric sounding system which has the ability of vertical incidence (?), oblique incidence (OI) and backscatter sounding (BS). WISS can record ?,OI and BS ionograms by sweep-frequency sounding. Inversion of the ionograms obtained by WISS enable it monitors the ionospheric electron density distribution of the sounding area much better. Furthermore, the application value of WISS can also be expanded by inversion of the ionograms obtained by WISS. The purpose of this paper is to support the Over The Horizon Radar (OTHR) coordinate registration, High Frequency (HF) communication frequency selection, the Total Electron Content (TEC) estimation, and ionospheric monitoring for earthquake precursor and so on by inverting the ?,OI and BS ionograms recorded by WISS. The research achievement of this paper is shown below.1) Designed and developed a software named WissViewWissView is a software used to control WISS to carry out sweep-frequency ionospheric sounding in order to obtain the high quality ionograms which can be inverted to electron density profiles. The software, with features of clear structure, strong scalability and high rate of code reuse, is designed and developed using object-oriented method. In terms of control flow design, WissView adopts the multi-threading technology to avoid the software user interface appears the phenomenon of "suspended animation" when detection is carrying out; In terms of data processing and display, the application of the Matrix <LIB> matrix library effectively overcomes the shortcomings of Visual C++in scientific computing and data visualization, reduces the difficulty of development and improves the efficiency of development; The remote control function of WissView enables WISS have the ability of network detection; The file transfer capability of WissView enables the ionograms recorded by the distant sounding stations to be send back automatically to the server in real time. And a large number of actual detection proves that WissView can operate reliably, and can provide a large number of high-quality ionograms for the purpose of electron density profile inversion. At present, the software has been used for the ionospheric sounding carried out by the ionosphere laboratory of Wuhan University, Seismological Bureau of Sichuan Province Xichang earthquake central station and Yunnan Pu'er Seismological Bureau. The backscatter sounding data processing section of this software has been successfully applied to a vehicle-mounted single station shortwave frequency selection system.2) Inversion of WISS ionogramsBecause the convergence performance of the linear decreasing weight particle swarm optimization (LDWPSO) algorithm is better than the simulated annealing algorithm and basic particle swarm optimization algorithm, so the LDWPSO algorithm is selected to invert the WISS ionogram. And the a posterior probability density is used to evaluate the inversion results. The algorithm is robust, converges fast, can find the global optimal solution of the inversion results with high probability, and easy to program.The WISS ? ionogram inversion algorithm uses the QPS model to characterize the ionospheric electron density profile. The inversion algorithm begins with the inversion of the ? echo reflected from the E layer, then inverts the VI echo reflected from the F1layer, finally inverts the VI echo reflected from the F2layer. And the whole electron density profile can be obtained after the QPS model parameters of each layer are inverted. The critical frequency of each layer is determined directly from the VI ionogram, so the inversion algorithm only needs to solve for peak height and semi-thickness. The inversion algorithm requires two data points from each layer, but the frequency interval of the two points selected can not be too small. The results of analysis of the ideal synthesized ionogram with no noise show that inversion results equal to the real value; The results of analysis of the synthesized ionogram with noise show that the differences of inversion results and the real value are very small, so the noise immunity of the inversion algorithm is very good; The results of analysis of typical day and night WISS ? ionograms show that the accuracy of the algorithm is very high.The WISS OI ionogram inversion algorithm also uses the QPS model to characterize the electron density profile of the ionosphere corresponding to the mid-point of the oblique link. The OI ionogram inversion algorithm also begins with the inversion of the OI echo reflected from the E layer, then inverts the OI echo reflected from the F1layer, finally inverts the OI echo reflected from the F2layer. And the whole electron density profile of the ionosphere corresponding to the mid-point of the oblique link can be obtained after the QPS model parameters of each layer are inverted. Because the critical frequency of each layer cannot be determined directly from the01ionogram, so the inversion algorithm requires three data points from each layer. Both the ray path geometry relation and the equation of ray path are used for obtaining the exact solution of the elevation angle. The results of analysis of the ideal synthesized ionogram with no noise show that inversion results almost equal to the real value; The results of analysis of the synthesized ionogram with noise show that the differences of inversion results and the real value are small, so the noise immunity of the inversion algorithm is good; In addition, the algorithm is proved to be suitable for experiment data inversion by comparing the inversion results obtained from the OI ionogram inversion algorithm and VI ionogram inversion algorithm.Take into account the HF radar backscatter inversion technology is to be applied to a vehicle-mounted system, so the leading edge of the sweep frequency backscatter ionogram is used for the purpose of electron density profile inversion. WISS can only recorded leading edge corresponding to the echo backscattered from F layer (or F2layer), so only recorded leading edge corresponding to the echo backscattered from F layer (or F2layer) is need to be inverted. At the beginning, the single QP model is used to characterize the vertical distribution of the ionospheric electron density. Later, taking into account the impact of the lower ionosphere on radio wave propagation, the research of inversion with the QPS model is made. At the lower left-hand corner of the backscatter ionnogram is seen the VI echo, which could be obtained because some energy does escape from the antenna in a vertical direction. The parameters of lower ionospheric layer (E layer or E layer, F1layer) can be obtained inverting the local VI echo. However, the parameters of lower ionospheric layer can be obtained from the IRI model if the local VI echo trace is incomplete or totally not observed. The2D electron density distribution in a vertical plane aligned in the direction of sounding can be obtained after the whole leading edge has been inverted. The results of analysis of the ideal synthesized ionogram with no noise show that inversion results almost equal to the real value; The results of analysis of the synthesized ionogram with noise show that the differences of inversion results and the real value are small, so the noise immunity of the inversion algorithm is good; In addition, the results of analysis of Wuhan and Qingdao experiment show that the accuracy of the algorithm is very high. At present, the inversion algorithm has been successfully applied to a vehicle-mounted single station shortwave frequency selection system.