Observations of strong radar returns from the high latitude F-region using the CUTLASS radar

Strong returns from the Finland component of CUTLASS were observed to occur in the far ranges, which correspond to latitudes 70 degrees-85 degrees Delta. An important goal of the SuperDARN network of radars is to characterise the very high latitude ionospheric motion. It is therefore important to understand when and why data is recorded from these far range gates. To achieve this a statistical study of the seasonal, UT and IMF dependence of the enhanced backscatter is performed. A clear seasonal dependence is observed with enhanced backscatter being seen predominantly in the winter with no events occurring in the summer. Using ray tracing techniques it is shown that this dependence is related to propagation effects. There is also a clear dependence on the IMF B-z component, with structure occurring predominantly under northward B-z. No dependence on B-x or B-y is observed. The location an event is first observed has a seasonal dependence with events first being seen from 8 - 12 MLT in the equinox periods and 12 - 14 MLT in the winter. (C) 1998 COSPAR. Published by Elsevier Science Ltd.