Improved method to derive equivalent current systems from global MHD simulations  

作　　者：ZHANG JiaoJiao WANG Chi TANG BinBin 

机构地区：[1]State Key Laboratory of Space Weather, Center for Space Science and Applied Research, Chinese Academy of Sciences [2]University of Chinese Academy of Sciences

出　　处：《Science China Earth Sciences》2014年第1期167-173,共7页中国科学（地球科学英文版）

基　　金：supported by the National Basic Research Program of China(Grant No.2012CB825602);National Natural Science Foundation of China(Grant Nos.41231067&41204110); in part by the Specialized Research Fund for State Key Laboratories of China

摘　　要：Derivation of equivalent current systems(ECS)from a global magnetospheric magnetohydrodynamics(MHD)model is very useful in studying magnetosphere-ionosphere coupling,ground induction effects,and space weather forecast.In this study we introduce an improved method to derive the ECS from a global MHD model,which takes account of the obliqueness of the magnetic field lines.By comparing the ECS derived from this improved method and the previous method,we find that the main characteristics of the ECS derived from the two methods are generally consistent with each other,but the eastward-westward component of the geomagnetic perturbation calculated from the ECS derived from the improved method is much stronger than that from the previous method.We then compare the geomagnetic perturbation as a function of the interplanetary magnetic field(IMF)clock angle calculated from the ECS derived from both methods with the observations.The comparison indicates that the improved method can improve the performance of the simulation.Furthermore,it is found that the incomplete counterbalance of the geomagnetic effect produced by the ionospheric poloidal current and field-aligned current(FAC)contributes to most of the eastward-westward component of geomagnetic perturbation.Derivation of equivalent current systems （ECS） from a global magnetospheric magnetohydrodynamics （MHD） model is very useful in studying magnetosphere-ionosphere coupling, ground induction effects, and space weather forecast. In this study we introduce an improved method to derive the ECS from a global MHD model, which takes account of the obliqueness of the magnetic field lines. By comparing the ECS derived from this improved method and the previous method, we find that the main characteristics of the ECS derived from the two methods are generally consistent with each other, but the east- ward-westward component of the geomagnetic perturbation calculated from the ECS derived from the improved method is much stronger than that from the previous method. We then compare the geomagnetic perturbation as a function of the inter- planetary magnetic field （IMF） clock angle calculated from the ECS derived from both methods with the observations. The comparison indicates that the improved method can improve the performance of the simulation. Furthermore, it is found that the incomplete counterbalance of the geomagnetic effect produced by the ionospheric poloidal current and field-aligned current （FAC） contributes to most of the eastward-westward component of geomagnetic perturbation.

关 键 词：equivalent current systems global MHD model improved method 

分 类 号：P318[天文地球—固体地球物理学] O361.3[天文地球—地球物理学]