CUTLASS FINLAND RADAR OBSERVATIONS OF THE IONOSPHERIC SIGNATURES OF FLUX-TRANSFER EVENTS AND THE RESULTING PLASMA FLOWS

The CUTLASS Finland radar has been run in a two-beam special scan mode , which offered excellent temporal and spatial information on the flow s in the high-latitude ionosphere. A detailed study of one day of this data revealed a convection reversal boundary (CRB) in the CUTLASS fie ld of view (f.o.v) on the dayside, the direction of plasma flow either side of the boundary being typical of a dawn-cell convection pattern. Poleward of the CRB a number of pulsed transients are observed, seemi ngly moving away from the radar. These transients are identified here as the ionospheric signature of flux transfer events (FTEs). Equatorwa rd of the CRB continuous backscatter was observed, believed to be due to the return flow on closed field lines. The two-beam scan offered a new and innovative opportunity to determine the size and velocity of t he ionospheric signatures associated with flux transfer events and the related plasma flow pattern. The transient signature was found to hav e an azimuthal extent of 1900 +/- 900 km and an poleward extent of sim ilar to 250 km. The motion of the transient features was in a predomin antly westward azimuthal direction, at a velocity of 7.5 +/- 3 km.