Study On Regional Ionospheric Characteristics Based On Technique Of Ground-based GPS And Radio Occultation

As an important part of the space environment, the ionosphere is a part of the upper atmosphere of the earth and related to people's lives closely. The ionosphere can be used as a protective layer of the earth to protect all kinds of creatures from the solar and cosmic radiation. At the same time, it has a significant effect on the propagation of electromagnetic waves in the atmosphere, which makes the propagation of electromagnetic wave, reflection, refraction, absorption and other effects. The ionosphere has an important influence on radio communication, navigation, measurement and others human space activities. Therefore, it has important scientific significance and application value to analyze and study the changes of the ionospheric characteristics. Polar regions are earth geographic pole and geomagnetic poles common location, special geographical location and the day the earth space environment determines the ionosphere in the region has a certain particularity, has become the key area of the earth space physics research.With the development of radio communication technology and the increasing development of human space exploration activities, people's desire and demand for the complex space environment is becoming stronger and stronger. With GPS technology unceasing development, the application method and the method of continuous expansion, with the implementation of China's national base station network, combined with Radio Occultation technology continues to improve, makes GPS technology becomes the detection and study of the ionospheric new important technical means, wide attention and research in the subject to atmospheric space measurement, space physics and other fields. For in the different space physics environment and different regional geographic location, the ionospheric characteristics will exhibit different change rules and characteristics of, with significant spatial and temporal variation characteristics. Based on the above background, in this paper, comprehensive utilization of ground-based GPS and occultation technique, select the typical low latitude area (Wuhan) or in the high latitude area (Antarctica), the ionospheric characteristic parameters extraction based on multi-source GPS observation data and ionospheric function fitting model and of ionospheric variation and temporal and spatial distribution were analyzed. The research work of this paper mainly includes the following contents:(1) Modeling and obtaining high precision ionospheric TEC based on GPSThe method and process of the GPS method and the process of the ionospheric TEC are introduced, which emphasizes the importance of the carrier phase smoothing pseudo range and the accuracy of the hardware delay. Based on the realization of high precision modeling, the fitting precision of three kinds of single layer models, such as polynomial function, generalized trigonometric function and low order spherical harmonic function, is compared with the results of GIM CODE.(2) Analysis of the changes of the TEC in the Wuhan region during the last solar cycleUsing polynomial function to establish a single-layer ionosphere TEC model in Wuhan area, ionospheric TEC for near a solar cycle in Wuhan area are obtained. Then, the seasonal and daily variation of TEC, the abnormal changes of the half of the year in Wuhan area are analyzed.(3) High precision ionospheric TEC application to the case of an earthquake ionospheric anomaly detection and analysisBy ground-based GPS observation data and single layer ionosphere model, the foreshock ionospheric TEC is obtained from the position of Lushan earthquake, earthquake in Nepal, the California earthquake. Using a combination of sliding window and quartile of statistical methods, excluding solar and geomagnetic activity effects on the ionospheric disturbances, we find that on the three times before the earthquake ionospheric variation detection, Lushan, Nepal earthquake occurred significant ionospheric anomalies. The changes and spatial distribution characteristics of ionospheric anomalies before two earthquakes are analyzed with CODE GIM data.(4) The spherical cap harmonic analysis theory and method into the research on Modeling of ionospheric TEC in AntarcticaThe spherical cap harmonic analysis theory and method into the research on Modeling of ionospheric TEC in antarctica. The Antarctic region of ground-based GPS data, the Antarctic ionosphere TEC model is established, will be based on the spherical cap harmonic function to get the Antarctic regions of the ionosphere TEC and other function model fitting results are compared and combined with the physical meaning of the spherical cap harmonic model of the zero order coefficients, the spectrum characteristics were analyzed. To explore the Antarctic region as a whole and local geographical position of Ionospheric TEC seasonal changes, diurnal variation, analysis found that the Weddell Sea anomalies are discussed. The physical mechanism of the occurrence of the brief explanation.(5)The analysis of characteristics changes of the topside ionosphere in Antarctic based on GPS Radio Occultation techniqueAfter two GPS Occultation inversion of ionospheric electron density Abel integral method introduced in detail, using vertical measurement instrument measured and IRI model data in which a common integral transform method was verified. The COSMIC Radio Occultation data inversion of the Antarctic region of the ionospheric electron density profile, hmF2, NmF2, VSH and ionospheric parameters are extracted and solar activity in low and high years during the Antarctic region in the topside ionosphere changes were studied, discussed the F2 layer in the solar cycle variation, interannual variation, diurnal changes, and an analysis of the vertical structure characteristics of Antarctic region in the topside ionosphere, especially in the Weddell Sea variation anomaly in the vertical direction.