Properties of Field Aligned Current in Plasma Sheet Boundary Layers in Magnetotail: Cluster Observation

Field aligned current (FAC) distribution in the plasma sheet boundary layers (PSBLs) in the magnetotail is studied statistically by analysing magnetic field data from the Cluster 4-point measurements. The results show that the FAC distribution on the dusk side is not the same as that on the dawn side in the magnetotail. On the each side earthward and tailward, FAC occurrences are different; occurrence and average current density of FACs in the northern hemisphere are different from those in the southern hemisphere. This implies that the FACs have dusk-dawn side asymmetry, polarity asymmetry and inter hemisphere difference in the magnetotail. The present results give a good observation evidence for study on the FAC mechanism.