对流电场、场向电流和极光区电集流变化的地磁响应  

GEOMAGNETIC RESPONSES TO THE CONVECTION FIELD,FIELD-ALIGNED CURRENT AND AURORAL ELECTROJET

作　　者：沈长寿[1] 资民筠[2] 高玉芬[3] 索玉成[4] 吴健[4] 

机构地区：[1]北京大学地球物理系,北京100871 [2]中国艺术研究院,北京100009 [3]中国地震局地球物理研究所,北京100081 [4]电子工业部中国电波传播研究所,新乡453003

出　　处：《地球物理学报》1999年第6期725-731,共7页Chinese Journal of Geophysics

基　　金：国家自然科学基金!49674245

摘　　要：对流电场、场向电流和极光区电集流是磁层一电离层耦合的主要物理过程．它们的演化发展时间分别为几分钟至半小时的量级．本文用１００°Ｅ和３００°Ｅ的两个地磁经度链附近各１１个台站的１ｍｉｎ均值地磁Ｈ和Ｚ分量资料，分析了１９９４年４月１６—１７日磁暴期间磁层耦合过程对极光区和中低纬区电离层扰动的地磁特征．强磁暴开始时，台站所处的地方时位置不同，则观测到的电离层和地磁响应也完全不同．这是磁层对流和一、二区场向电流共同作用的结果．一般说，扰时极光区的西向电集流变化更为强烈．随着耦合的发展，极光区范围会向南北扩展，电集流中心带则向低纬侧移动．在中低纬区，二区场向电流的建立能屏蔽一区场向电流所产生的扰动，并引起反向的电流及地磁变化．由此，中低纬区夜间有可能出现短时间的东向电场，又可通过ＥＸＢ的垂直向上漂移作用抬升Ｆ层等离子体，并发生同一经度链附近的多站电离层ｈ＇Ｆ同时突增现象．另一方面，磁赤道附近的台站则更多地受内磁层赤道环电流和电离层赤道电集流的影响．Convection field, field-aligned current and auroral electrojet are all very importentprocesses in the magnetosphere-ionosphere coupling. The time scale of their evolutionis about several minutes to half an hour. In this paper geomagnetic data of H andZ-component with time resolution of one minute from each 11 stations nearby 100 EGM and 300 E GM meridians are used to analyze the effect of magnetospheric disturbance on geomagnetic features of the auroral electrojet and disturbed currents inmid-and low-latitude ionospheres during a magnetic storm on April 16-17, 1994. Itis shown that the geomagnetic response of the magnetosphere-ionosphere coupling isrelated to the local time zone of the station. ms is caused by the combined effectsof the magnetospheric convection pattern and the field-aligned current systems. Duringa magnetic storm, genarally speaking, the variation of the westward auroral electrojetis the stronger one, and the auroral region may expand both poleward andequatorward. Besides, the center belt of the electrojet will move toward lower latitude.At the mid-latitude ionosphere the establishment of the region 2 field-aligned currentwill shield the disturbance caused by the region 1 field-aligned current and produce areversed current leading to a reversed geomagnetic field. These may cause a shorttime increasing of a eastward electric field at night side. As a result thesimultaneously h' F (minimum vertual height for F-region) enhancement due to theE X B drift effect will be observed at several stations nearby a meridian. On the otherhand, variations of geomagnetic field near the equator area are mainly influenced bythe ring current and the ionospheric equatorial electrojet.

关 键 词：地磁响应 对流电场 场向电流 极光区电集流 

分 类 号：P318.24[天文地球—固体地球物理学] P318.22[天文地球—地球物理学]