Field-Aligned Currents at the PSBL on 17 August 2001 Storm: Relationships with solar Wind Conditions

Using magnetic field and plasma data acquired with Cluster spacecrafts, we investigate the relationship between the field-aligned currents (FACs) at the plasma sheet boundary layer (PSBL) and solar wind dynamic pressure, as well as the interplanetary magnetic field (IMF) B(y) on 17 August 2001 storm. Our studies reveal that FAC density at the PSBL in the magnetotail in the storm time is controlled mainly by the solar wind dynamic pressure rather than IMF B(y) The FACs at the PSBL are associated with the low-altitude region-1 current and have the same polarity as region-1 current in the dawn sector. In the polar region, the footprints of the FACs at the PSBL expand equatorward. The data analysis also shows that a very strong FAC with a density over 40 nA.m(-2) appeared in this storm time when a substorm just occurred.