Ionospheric Currents and F-Region Plasma Boundaries Near the Dayside Cusp

Observational evidence of the location of a dayside high-latitude ionospheric current (DPY current) with respect to the different regimes of the high-latitude magnetosphere is obtained by analyzing data from the magnetometer chain along the west coast of Greenland in conjunction with simultaneous measurements from the newly established incoherent-scatter radar facility at Sondre Stromfjord. The latitudinal location of the DPY current is compared with the location of the maximum F-region electron temperature and with the location of the plasma convection reversal from sunward to antisunward. The maximum in the F-region electron temperature roughly coincides with the velocity reversal boundary, while the DPY current is always located more poleward, penetrating deep into the polar cap. When UT variations are examined, a correlation of 70 to 80 percent is found between the three locations.