Using the east-west geomagnetic disturbance fields observed from stations at mid-latitudes,we investigate the characteristics of field-aligned currents on the nightside during the April 6,2000 superstorm.The results indicate that there is an eastward disturbance on the nightside of Northern Hemisphere during the main phase of magnetic storm,while the interplanetary magnetic field(IMF)is continued southward.The positive disturbances in the postmidnight are larger than that in the premidnight.This suggests that upward field-aligned currents develop on the nightside,when the IMF is directed southward.The peak of upward fieldaligned currents is located in postmidnight,and it will be more obvious at substorm expansion.We get the conclusion that both partial ring current and region-2 field-aligned current shift to dusk sector.The upward region-2 current is decreased at substorm onset,and intensified after it.We also investigate the relationship between the upward field-aligned currents on the nightside and the auroral electrojets at high latitudes.It shows a good correspondence between region-2 current and the westward electrojet in the postmidnight.We suppose that they are both associated with the convection electric field.
WANG YuanHONG MingHuaCHEN GengXiongXU WenYaoDU AiMinZHAO XuDongLIU XiaoCanLUO Hao
Using the east-west geomagnetic disturbance fields observed from stations at mid-latitudes,we investigate the ...
WANG Yuan~(1,2),HONG MingHua~(1*),CHEN GengXiong~1,XU WenYao~1,DU AiMin~(1,3), ZHAO XuDong~(1,2),LIU XiaoCan~4 & LUO Hao~(1,2) 1 Institute of Geology and Geophysics,Chinese Academy of Sciences,Beijing 100029,China
It is believed that a southward interplanetary magnetic field (IMF) is mainly responsible for the energy input from solar wind into the magnetosphere.This paper presents an unusual case of strong anti-sunward plasma flow (up to 2 km/s) in the polar cap ionosphere and large cross-polar cap potential (CPCP) during a period of horizontal IMF (|BZ| < 2 nT) observed by both ACE (at the L1 point) and Geotail (on the dusk flank of the magnetosheath).The CPCP is even higher than that under preceding BZ ≈-23 nT.Furthermore,GOES8 observed that the magnetosheath field turns northward as the anti-sunward plasma flow and CPCP start to increase,which implies that the magnetosheath field interacting with the Earth's magnetopause has significantly rotated and differs from the IMF observed by ACE and Geotail.In accordance with previous theoretical work,we suggest that the magnetic field line draping produces a southward magnetosheath field and enhances anti-sunward plasma flow and the CPCP.
It is believed that a southward interplanetary magnetic field（IMF） is mainly responsible for the energy input ...
WEI Yong~(1,2),ZONG QiuGang~2,PU ZuYin~2,WAN WeiXing~(1*),LIU JianJun~3,FU SuiYan~2 & SHI QuanQi~4 1 Beijing National Observatory of Space Environment,Institute of Geology and Geophysics,Chinese Academy of Sciences,Beijing 100029,China
