Region 1 Birkeland Currents from a Global MHD Simulation of the Magnetosphere.

The study of large scale geomagnetic field aligned currents, which couple the dynamics of the magnetosphere and the high latitude ionosphere, has been an area of intense research interest in recent years. These currents, first postulated by Birkeland 1908 to be responsible for geomagnetic activity and auroral phenomena in the polar regions, were first observed in the 1970s by Arnoldy, Zmuda and Armstrong and Sugiura and have now been extensively measured and documented by satellite and rocket magnetometers. The large scale Birkeland currents are observed in two rings which encircle the polar regions. The poleward ring has been called the Region 1 system and the equatorward ring the Region 2 system. Global numerical MHD simulation data for the earths magnetosphere has been used to calculate Birkeland current systems in the polar ionosphere. In this report, we show the results for the Region 1 Birkeland currents. We demonstrate how the currents are organized on open or closed field lines in daytime and nighttime sectors. The current source regions are identified and driving mechanisms are discussed.