Birkeland currents in the earth's magnetosphere

Satellite observations of the large-scale patterns, flow directions, and intensities of Birkeland currents in the auroral and polar regions and their relationship to the orientation and magnitude of the IMF are reviewed. Viking and AMPTE/CCE observations have provided evidence for resonant Alfven waves on the same geomagnetic field lines that guide stationary Birkeland currents. The observations suggest that Birkeland currents play an important role in the coupling of energy between the interplanetary medium and the lower ionosphere and atmosphere.