Large scale structures of the convection inferred from coordinated measurements by EISCAT and GEOS 2

The equipotential lines of the ionospheric convection electric field can be derived from F-region ion drift measurements performed by EISCAT during 24 h latitudinal scans across the auroral zone. The plasmapause location can be identified with the outermost closed equipotential line from the flow pattern, taking into account the corotation electric field. This indirect prediction is compared with plasmapause crossings simultaneously observed at the geostationary orbit by the spacecraft GEOS 2 located in the vicinity of the apex of the EISCAT magnetic field line. The agreement between these two experimental results validates the method inferred from EISCAT F-region ion drift measurements. In addition, it demonstrates the capability of the EISCAT system to reproduce correctly the large scale structures of the magnetospheric convection over a wide equatorial region from about 4 to 10 earth radii.