STARE: Observations of a field-aligned line current

For the first time a magnetospheric line current entering the ionosphere ha s been unambiguously observed. The observation was made with STARE ( = Scan dinavian Twin Auroral Radar Experiment), a ground based coherent radar syst em, which has been updated with modern computer technique, and recently tak en into operation. A counter clockwise turning swirl of ionospheric electro n drift velocities is synonymous with the presence of a line current Rowing along the geomagnetic field lines into the ionosphere. A Flux Transfer Eve nt on the magnetopause has been predicted to connect to the ionosphere via a line current.