磁暴期间极区电离层等效电流无旋分量变化1.个例分析  

Variation of the curl-free component of ionospheric equivalent current in the Arctic during storms 1.Case analysis

作　　者：葛攀泽 李汇军 成巍 黄莹莹 王承志 GE PanZe;LI HuiJun;CHENG Wei;HUANG YingYing;WANG ChengZhi(Nanjing University of Aeronautics and Astronautics,Academy of Astronautics,Nanjing 210019,China;Institute of Applied Meteorology,Beijing 100029,China;Wuhan University,Wuhan 430072,China)

机构地区：[1]南京航空航天大学航天学院,南京210019 [2]北京应用气象研究所,北京100029 [3]武汉大学电子信息学院,武汉430072

出　　处：《地球物理学报》2024年第7期2506-2518,共13页Chinese Journal of Geophysics

基　　金：面上基金(41775039,41375045);青年基金(40904048);国家重点研发计划(2018YFC1506201)共同资助。

摘　　要：磁暴期间极区电离层电导率分布发生变化,导致场向电流和电离层电流无旋分量形成的电流回路也随之发生复杂变化.通过地磁反演获取极区电离层等效电流,有助于分析磁暴期间上述电流回路变化规律.本文应用低秩近似方法实现了极区INTERMAGNET地磁台网磁扰观测资料的反演,获得了2015年9月20日、11月30日两次典型磁暴活动期间北半球极区电离层等效电流信息,重点考察了无旋分量在磁暴期间变化规律.主要结论有:电离层等效电流包含无源分量和无旋分量,磁暴期间总体呈现为无源分量主导,无旋分量占比较少的特征;磁暴急始阶段,地磁场扰动源主要来自磁层顶,电离层电流没有明显变化;磁暴主相阶段,极区电离层等效电流无源分量呈双涡结构,与以往的研究一致,而无旋分量主要由晨侧流向昏侧;恢复相阶段,极区地磁活动减弱,等效电流无源分量双涡结构发生演化,无旋分量中由日侧流向夜侧的电流成分增加;恢复相后期等效电流无旋分量主要由昏侧流向晨侧,与主相时相比流向相反.无旋电流流向的变化能够反映场向电流在电离层中的闭合电流的总体流向变化,流向出现反转可能是受场向电流变化的影响.In the Arctic region,a dynamic interplay between field-aligned current and the curl-free component of the ionospheric current forms a current loop.This loop undergoes intricate changes during magnetic storms due to fluctuations in ionospheric conductivity.Understanding these alterations requires a comprehensive analysis of ionospheric equivalent current inversion alongside geomagnetic observations.In this study,we undertake the inversion of ionospheric equivalent current utilizing data from the INTERMAGNET geomagnetic network during two significant storm events on September 20,2015,and November 30,2015.Employing low-rank approximation analysis,we delineate the ionospheric equivalent current into its divergence-free(essential component)and curl-free components.Our findings reveal that during sudden storm commencements(SSC),there's no notable change in the ionospheric current.However,during the main phase of magnetic storms,the divergence-free current exhibits a DP2 structure,consistent with previous research,while the curl-free current predominantly flows from the dawn side to the dusk side.In the subsequent recovery phase,this flow shifts from the dayside to the nightside.Interestingly,in the later stages of the storms,the curl-free current reverses direction,flowing primarily from the dusk side to the dawn side,contrasting with its behavior in the main phase.This reversal suggests a dynamic alteration in the near current of field-aligned current within the ionosphere,particularly in regions 1 and 2.

关 键 词：电离层等效电流 极区电离层 地磁观测 低秩近似分析 

分 类 号：P352[天文地球—空间物理学]