IMF By Influence on Magnetospheric Convection in Earth's Magnetotail Plasma Sheet

Abstract

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⊥xy<200 km/s) in the magnetotail plasma sheet under the influence of a clearly nonzero dawn-dusk interplanetary magnetic field (IMF By). We find that IMF By causes an interhemispheric asymmetry in the flows, which depends on the direction of IMF By. 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 By reveals that the region where the asymmetry in the average flows appears agrees with the appearance of the tail By direction collinear to IMF By. The results imply that IMF By has a major influence on the direction of the magnetic flux transport in the magnetotail.