资源环境科技发展态势分析平台

We use Geotail, Cluster, and Time History of Events and Macroscale Interactions during Substorms data over 15 years (1995-2009) to statistically investigate convective ion flows (V-perpendicular to xy<200 km/s) in the magnetotail plasma sheet under the influence of a clearly nonzero dawn-dusk interplanetary magnetic field (IMF B-y). We find that IMF B-y causes an interhemispheric asymmetry in the flows, which depends on the direction of IMF B-y. On the average, one magnetic hemisphere is dominated by a dawn-dusk flow component, which is oppositely directed compared to that in the other hemisphere. This asymmetry is observed for both earthward and tailward flows. A comparison to tail B-y reveals that the region where the asymmetry in the average flows appears agrees with the appearance of the tail B-y direction collinear to IMF B-y. The results imply that IMF B-y has a major influence on the direction of the magnetic flux transport in the magnetotail.