极光活动的季节与经度变化及其电离层热层效应研究

Previous studies have shown that the frequency and intensity of the auroral precipation depends highly on the geomagnetic activity and the solar wind/interplanetary magnetic field (IMF) conditions. Also, it was found that the aurora precipitation vary with season and longitude and hemisphere. However, there is very little study involving in these variations and their related mechanisms under geomagnetically disturbed conditions, due to very limited observations. In this project, we will combine both the observation from TIMED/GUVI and POLAR/UVI to study auroral variations under geomagnetically disturbed conditions. Firstly, the auroral energy flux derived from TIMED/GUVI and POLAR/UVI observational images will be compared and adjusted to similar level. Then we will study the seasonal and longitudinal variations of the auroral precipitation under Kp 4-7 or even higher Kp conditions, and also the dependence of these variations on the geomagnetic activity and the solar wind/IMF. The relative roles of the solar flux, geomagnetic field and solar wind/IMF on the auroral variations will be discussed. Further, we will construct an empirical model of the auroral oval, to consider the longitudinal, seasonal and hemispheric variation patterns of auroral precipitation. Finally, we will put this model to the NCAR-TIEGCM to simulate its effects on the ionosphere and thermosphere. The roles of the auroral variations on special phenomena in the ionosphere and thermosphere will be discussed too, such as the night time enhancements of the electron density and the longitudinal structure of the neutral wind in the F region.

极光活动不但随地磁活动和太阳风/行星际磁场强烈变化，而且具有显著的经度和季节等变化特征。受观测不足所限，以往对地磁扰动条件下极光活动的变化特征及其相关物理机制的研究较为缺乏。本项目拟融合TIMED/GUVI和POLAR/UVI在1996-2008期间近一个太阳活动周期的极光成像观测，获取不同地磁扰动条件下的观测样本，研究极光粒子沉降能量随经度和季节的变化特征，重点分析Kp 4-7或更强磁扰条件下的极光活动变化。同时，探索影响极光活动经度与季节变化的太阳辐射通量、地磁场位形以及太阳风-行星际磁场的相对贡献。另外，本项目拟建立极光椭圆内粒子沉降能量随经度和季节等变化的经验模型，并将其引入三维大型理论模式（如NCAR-TIEGCM）内嵌的极光模型中，研究极光活动上述变化对电离层热层影响的程度和范围及其对电离层热层现象的可能贡献。

本项的目的是聚焦于极光活动的季节与经度变化，并考察其电离层热层效应。拟研究内容包括多星极光成像数据的融合，在此基础上研究极光粒子沉降能量的空间分布随太阳活动、地磁活动、行星际磁场条件等因素的变化，并探讨其电离层效应，以深入探讨磁层与极区电离层/热层耦合机制，为空间天气建模和预报服务。在本项目实施的四年过程中，通过融合TIMED/GUVI极光成像仪和近年来才发布的多个DMSP/SSUSI极光成像仪的观测，获取了超过一个太阳活动周的沉降能量观测，积累了长期和海量的沉降通量数据源，并获得了较好的扰动时期的时空覆盖；结合COSMIC掩星星座在极区电离层的观测，围绕本项目提出的研究目标和内容，获得了大量新的研究结果。其主要成果包括对比分析了粒子沉降与极区电离层经度变化特征，揭示了以往因观测缺乏而尚不清楚的极区电离层气候学变化特征和南北半球不对称性及其成因，并阐明了粒子沉降能量与太阳辐射的相对贡献，以及粒子沉降与其电离层效应不一致之处等。在本学科主流国际杂志JGR上发表对本项目进行第一标注的SCI论文6篇，以及其它标注（第二、第三）形式的SCI论文6篇。培养硕士毕业生一名，在读硕士和博士生各一名。