电离层暴时响应的半球不对称性

The variability and drivers of the ionosphere during the magnetic storms are a hot and challenging issue in ionospheric physics. Many investigations have reported that there is a reasonable hemispheric asymmetry in the responses of the ionosphere during storms, even the storms occur during the equinoxes. Under the financial support of this project, we will study the hemispheric asymmetry in the storm-time responses of the ionosphere with case study, statistical study, and modeling. The topside ionosphere will be explored in terms of ground-based and satellite ionospheric data. The main issues focus on the responses of the topside ionosphere, including the unknown question, the ion species and its role in positive and negative phase storms. Comparative study will be conducted with that of the F peak to reveal the similarity and difference between the features of the topside and F peak. The investigations will give us some information on the hemispheric asymmetry of the storm-time topside and F peak ionosphere, and promote our understanding of the chemical and dynamical processes involved in the ionosphere at different altitudes during storms.

磁暴期间电离层行为及其机理是电离层物理的重要研究内容和热点之一。对系列空间天气事件的分析展示出电离层存在显著的南北半球不对称特征。本项目以典型磁暴事件电离层响应的南北半球不对称性为切入点，拟基于地基和卫星探测的电离层综合观测数据，采用事件分析、统计分析和模拟手段，以F层峰区和顶部电离层为研究对象，研究磁暴事件期间顶部电离层响应，研究顶部电离层离子成分特征及其在正负相电离层暴中所扮演的角色，并与F层峰区电离层暴时演化进行比对分析，揭示顶部电离层与F层峰行为的异同，来认知中低纬电离层在不同高度的南北半球不对称，进一步理解电离层化学与动力学过程对电离层正负相暴的作用。期望通过本项目的实施，拓展我们对中低纬顶部和F层峰电离层的暴时响应特征之异同及相关机理的认识。

项目以暴时中低纬电离层响应为核心科学问题，通过对地基和卫星探测综合观测的研究分析，揭示出在典型磁暴期间中低纬电离层响应存在明显的半球不对称特性与精细区域特征，发现磁暴驱动了从冬季半球指向夏季半球的扰动场向漂移；不同高度电离层的正负相暴响应存在时间、相位和幅度的差异；磁暴期间中纬电离层响应相位存在半球不对称，观测指示美洲扇区中纬电离层暴时响应存在以往未报道的强烈精细结构，伴随有电离层高度结构的改变。拓展到非磁暴期间电离层变化，发现曲靖到武汉一带存在有显著的电离层电子密度增强与强东西梯度特征，可能与赤道区电场的动力学驱动有关；对日食期间电离层的变化研究发现，日食区共轭半球影响依赖于磁力线长度；从中纬电离层剖面的经度结构研究发现，不同高度经度结构存在半球不对称性，导致南北半球经度结构可能源于低高度上磁位型引入光电离的经度差异，以及在220km以上区域与中性风相关的动力学控制。