小尺度电离层扰动是现代射电干涉仪和星载合成孔径雷达成像等的主要误差源,总电子含量（TEC）起伏是电离层扰动导致的相位误差的核心参量。建立和发展电离层扰动修正模型是问题解决的关键，缺乏对TEC起伏特性的把握是当前构建模型的瓶颈。因此，小尺度电离层扰动的TEC起伏特性研究是急需解决的关键科学问题。随着全球定位系统（GPS）的应用，利用局域或全球的GPS台网反演TEC、观测电离层扰动是最为重要和广泛采用的研究方法。本项目利用世界最密集的由上千台、平均间隔25 km的双频GPS接收机组成的GPS地球观测网（GEONET），发展具有高空间分辨率的TEC参量反演方法；提取小尺度电离层扰动TEC起伏及其特征参数，依此创立TEC起伏的空间统计模型；利用覆盖一个太阳周期的GEONET观测数据，研究小尺度电离层扰动TEC起伏的时变特性和空间演化，为建立小尺度电离层扰动修正模型奠定物理基础。

The small scale ionospheric disturbance is a major error to modern radio interferometer imaging and satellite aperture radar imaging. The total electron content (TEC) fluctuation is a key parameter in the phase error caused by the disturbance. An ionospheric disturbance correction model is crucial to remove the phase errors. However, there is a lack of understanding at the characteristics of TEC fluctuation in small scale ionospheric disturbance which is a bottleneck in constructing the correction model. With the application of the Global Positioning System (GPS), regional or global GPS network is the most important and prevalent method for TEC derivation and the ionospheric disturbance observation. This proposal aims to study the characteristics of TEC fluctuation in small scale ionospheric disturbance with the world's most dense GPS Earth Observation Network (GEONET). GEONET consists of more than 1000 dual frequency GPS receivers in which the average distance between two adjacent receivers is about 25 km. An algorithm will be proposed for TEC derivation with high spatial resolution. Characteristic parameters describing the TEC fluctuation will be retrieved. A spatial statistical model for TEC fluctuation will be developed. Spatial morphology and temporal variation of TEC fluctuation will be investigated with data covering a solar cycle. TEC fluctuation during geomagnetic storm will also be examined to clarify formation and evolution of storm time irregularities. The results of this study will provide the physical basis to develop a TEC fluctuation correction model for small scale ionospheric disturbance.