The large scale Birkeland current system in the polar region has been studied by using the UCR-T1 space simulation facility (diameter 1.3 m, length 11 m). Intense plasma flow simulating the solar wind interacts with the terrella magnetic field which simulates the planetary dipole field. The northward interplanetary magnetic field (BIMF) is simulated by an externally applied uniform magnetic field throughout the interaction chamber. Magnetic field measurements above the polar cap show that for the northward interplanetary magnetic field, a stable well-developed W pattern in the transverse component of magnetic field, prevails for the entire period of the interaction. These results have a remarkable similarity with the space observations obtained from the Magsat satellite data. The W pattern can be interpreted as an evidence for a large-scale Birkeland current system which may be associated with the field line reconnection in the magnetotail. ¿ American Geophysical Union 1989