亚极光区极化流发生期间电离层离子下行的统计  

Statistics of Ion Downward Flows in the Ionosphere during Subauroral Polarization Streams

作　　者：魏冬 於益群 WEI Dong;YU Yiqun(School of Space and Environment,Beihang University,Beijing 102206;Key Laboratory of Space Environment Monitoring and Information Processing,Ministry of Industry and Information Technology,Beijing 102206)

机构地区：[1]北京航空航天大学空间与环境学院,北京102206 [2]工业和信息化部空间环境监测与信息处理重点实验室,北京102206

出　　处：《空间科学学报》2022年第1期73-81,共9页Chinese Journal of Space Science

基　　金：国家自然科学基金项目资助(41821003,41974192)。

摘　　要：亚极光区极化流是地球磁层–电离层耦合过程中最重要的现象之一,对电离层具有重要的调制作用。多数情况下,亚极光区极化流发生时会伴随局地离子上行流动,目前已对其有充分的研究,但对离子下行的研究却甚少。本文分析了DMSP卫星在2001-2 015年间16个地磁暴中的观测数据,在483个亚极光区极化流事件中找到102个离子下行事件,并对其开展统计研究,分析离子下行在亚极光区极化流事件中的发生率,在南北半球的分布以及有助于离子下行形成的条件。结果表明:离子下行在亚极光区极化流事件中发生概率较小,离子下行事件的发生与分布具有比较明显的南北半球差异,并且亚极光区极化流的速度与离子下行速度具有高度相关性,表现为线性关系;而离子下行极有可能是因为双极扩散与地球重力共同作用而产生的,并且离子的热运动强弱对离子下行的速度大小也具有重要影响。这些研究结果有助于进一步理解亚极光区极化流对地球电离层动力学的调制作用。During geomagnetically disturbed times, enhanced westward plasma flows appear in the duskside subauroral ionosphere and are termed as Subauroral Polarization Streams(SAPS). SAPS are usually believed as one of the most important features of the magnetosphere-ionosphere coupling and play an important role in regulating the ionospheric dynamics. Generally, SAPS can give rise to local ion upward flows, but there are few studies on ion downward flows. Based on the observations of DMSP satellites during 16 magnetic storm from 2001 to 2015, we find 102 cases with ion downward flows in all the 483 SAPS events. The occurrence rate of ion downward flows, the distribution of ion downward flows in the Northern and Southern Hemispheres, and the favored conditions for the formation of ion downward flows are further analyzed in these SAPS events. The results show that the occurrence rate of ion downward flow is relatively low in SAPS events, and the number and distribution of ion downward flow events are different on the two hemispheres. A linear relationship is found between the SAPS and ion downward flow velocities. Furthermore, the formation of ion downward flow is most probably caused by the combined effects of ambipolar diffusion and gravity. The intensity of ion thermal movement has significant influence on the velocity of ion downward flow. These results will help us to further understand the regulating effects of SAPS on the ionosphere.

关 键 词：亚极光区极化流 离子下行 分布特征 统计研究 

分 类 号：P352[天文地球—空间物理学]