径向行星际磁场下的场向电流统计学研究  

STATISTICAL RESEARCH OF FIELD-ALIGNED CURRENTS UNDER RADIAL INTERPLANETARY MAGNETIC FIELDS

作　　者：曹雪[1] 刘丁维 黄韬[1] 张科灯 

机构地区：[1]武汉大学电子信息学院空间物理系,湖北武汉430072

出　　处：《极地研究》2016年第1期11-18,共8页Chinese Journal of Polar Research

基　　金：国家自然科学基金(41222030)资助

摘　　要：基于CHAMP卫星高精度磁场观测数据,对2001—2009年径向行星际磁场(RIMF,radial interplanetary magnetic fields)条件下的场向电流的分布特征进行了统计学分析,并与2001—2009年期间场向电流的平均强度进行了对比研究,结果表明:正午时刻场向电流的平均强度对地偶极子倾角有明显线性依赖,冬夏季电流强度比值约为3左右,RIMF条件下冬夏季比值降为2;相对年平均值来说,RIMF条件下行星际磁场总幅度、重联电场、太阳风动压均有所减小,AE指数减弱,Dst指数略有降低;在通常情形下重联电场是场向电流很好的控制参数,但是在RIMF下,重联电场不再与电流强度相关;北半球电流强度在向地IMF条件下大于向日IMF,而南半球则相反,虽然RIMF条件下场向电流的均值小于年平均值,但是正午时段场向电流强度大于年平均值的概率大约为0.2,RIMF条件下仍然有地磁扰动事件(比如亚暴事件)发生。The characteristics of field-aligned currents（ FACs） and the related physical quantities under radial interplanetary magnetic field（ RIMF） from 2001 to 2009 were investigated. Statistical analysis and comparison with FACs under normal conditions were performed using CHAllenging Minisatellite Payload（ CHAMP） data. The results showed that the intensity of noon FACs has clear dependence on the dipole tilt angle under normal conditions and that the ratio between summer and winter is about 3; however,the dependence disappears under RIMFs and the ratio decreases to 2. The magnitude of the interplanetary magnetic field（ IMF）,the merging electric field,solar wind dynamic pressure,and the auroral electrojet（ AE） index decrease,while the disturbance storm time（ Dst）index remains almost stable under RIMFs. The merging electric field is a controlling factor of FACs under normal conditions,but the control effect disappears during RIMFs. In the Northern Hemisphere,the intensity of FACs under IMF Bx〈0 conditions is larger than that under IMF Bx〉0 conditions（ the situation is the converse in the Southern Hemisphere）. Although the intensity of FACs under normal conditions is greater than that under RIMFs,the probability that the density of FACs under RIMFs is greater than the yearly average is about 0. 2,and some geomagnetic disturbances,such as substorms,still occur under RIMFs.

关 键 词：场向电流 径向行星际磁场 重联电场 

分 类 号：P353[天文地球—空间物理学]