电离层中纬槽纬度结构时空变化特性的研究

The ionospheric mid-latitude trough is a large-scale depleted structure of ionospheric plasma density in the nightside F region for the sub-auroral latitudinal ionosphere. A lot of works are devoted to the investigations of the trough position and the occurrence rate of the trough, the investigations about the trough latitudinal structure are still needed to further explore. In addition, the low electron density, the strong horizontal electron-density gradients and the plasma irregularities in the trough region can obviously affect the radio wave signal. Therefore, the exact description and prediction of the trough latitudinal structure can improve the quality of the GPS navigation and positioning and radio communication. In this project the COSMIC Ne profiles and the DMSP & the Swarm satellites plasma density data are used to statistically study the dependence of the trough latitudinal structure in the latitudinal bands of 40°–80° on magnetic local time, longitude, season, solar activity level, geomagnetic activity level and altitude. A new empirical NmF2 model in the trough region is developed. In addition, the characteristics of the plasma temperature, drift velocity and Field-aligned Currents in the trough region are studied to explore the relationship between the mid-latitude trough structure and the structure of the plasma temperature, drift velocity and Field-aligned Currents. Our study is very important to investigate the characteristics of the mid- and high latitude ionosphere, model the ionosphere mid-latitude trough and understand the magnetosphere-ionosphere coupling mechanisms.

电离层中纬槽是亚极光纬度区域夜间F层典型的大尺度等离子体密度耗空结构。过去研究主要关注槽的极小位置及其发生率，缺乏对中纬槽纬度结构的形态学特征的全面认识。槽区低的电子密度、电子密度梯度边界以及经常出现的不规则体会显著影响无线电波信号的传播。中纬槽纬度结构的精确描述和预测有助于提高GPS导航定位和无线电通信质量。本项目拟基于COSMIC掩星观测和DMSP、Swarm卫星在轨探测的电离层数据，研究南北半球位于纬度40°到80°范围内的中纬槽纬度结构随地方时、经度、季节、太阳活动水平、地磁活动水平以及高度的变化特征，构建全球电离层中纬槽区的NmF2经验模式，分析中纬槽区等离子体温度、漂移速度和场向电流的变化特征，揭示中纬槽纬度结构与等离子体温度、漂移速度和场向电流结构间的关联性。本项目的开展对于认识中高纬电离层区域特性、中纬槽建模以及电离层-磁层耦合机制具有重要的科学意义和应用价值。

中纬槽是中纬电离层与高纬电离层的过渡区域，也是电离层与磁层耦合的关键区域，其纬度结构的研究对认识中高纬电离层区域特性、电离层与磁层耦合机制具有重要的科学意义。本项目基于收集整理的COSMIC、DMSP、Swarm卫星探测的电离层数据和TEC数据，统计研究了中纬槽和高纬槽纬度结构随经度、地方时、季节和太阳活动水平的变化特征，以及磁暴期间中纬槽纬度结构的变化特征；构建了全球中纬槽区的NmF2经验模式，模式计算的结果与观测统计结果基本一致；分析了亚极光电子温度增强的变化特征、中纬槽与亚极光电子温度增强的位置关系、以及中纬槽和高纬槽区场向电流和离子漂移速度分布特征，揭示了中纬槽纬度结构与等离子体温度、漂移速度和场向电流结构间的关联性，探索等离子体漂移速度和场向电流对中纬槽和高纬槽纬度结构的影响。研究结果提升了中高纬电离层的认识水平，发展了电离层亚极光区域经验模式，在导航定位和无线电通信等领域有一定的应用前景。