地球等离子体层是内磁层的重要组成部分，其密度结构在磁扰期间发生显著变化，这对内磁层和近地空间环境都有强烈的影响。我国自主研制的CE-3以及IMAGE卫星的EUV探测为等离子体层的研究提供了不同视角。但EUV探测数据仅代表探测器视野范围内三维空间离子在二维探测器平面内的密度累加，无法直接反映其沿探测方向不同深度的信息。为了更好的解读EUV探测数据，需将其反演为三维空间密度结构，但目前发展的各种反演算法都存在一定的局限性。因此，本项目将利用更具优势的CT方法对EUV探测数据进行反演，得到：1)磁平静期间稳态等离子体层的三维空间密度结构；2)磁扰期间等离子体层三维空间密度结构。通过对反演结果的比较分析，进一步得到：3)磁扰强度对等离子体层三维空间密度结构的影响；4)磁扰期间等离子体层密度结构的动态演化。以实现对等离子体层的密度结构及动态演化的深入认识，为磁层-电离层耦合机制的研究提供观测证据。

The earth’s plasmasphere is an integral part of the inner magnetosphere. Its density structure changes significantly during the period of magnetic disturbance, which has a strong influence on both the inner magnetosphere structure and the near-Earth space environment. The extreme ultra-violet (EUV) camera onboard the CE-3 lander and IMAGE satellite provides precious opportunity to study the plasmasphere. But the EUV images just reflect the 2D plane information, the scientists couldn’t directly obtain the information in different area of the plasmasphere. To better understand the EUV images, it is important to reconstruct the 3D spatial density structure from these 2D EUV images. Hence, a variety of reconstructing algorithms have been developed. Nevertheless, these algorithms have the own imperfections. So this project is focused on reconstructing the plasmaspheric density structure with the computed tomography (CT) algorithm, which is more advantageous than others. Through the CT reconstruction, to obtain: 1) steady plasmaspheric 3D spatial density structure; 2) plasmaspheric 3D spatial density structure during the period of magnetic disturbance. Through further analysis of the reconstructing results, to reveal 3) the influence of the plasmaspheric 3D spatial density structure under different geophysical conditions; 4) plasmaspheric dynamics of 3D spatial density structure during the period of magnetic disturbance. Based on these works, we may have a deep insight into the plasmaspheric dynamic process and its density structure, and hence, to provide observational evidence for the study of magnetospheric-ionospheric coupling mechanism.