THE PHASE SPEED OF ARTIFICIAL FIELD-ALIGNED IRREGULARITIES OBSERVED BY CUTLASS DURING HF MODIFICATION OF THE AURORAL IONOSPHERE

The RF heater facility at Ramfjordmoen, Tromso can generate field-alig ned plasma irregularities in the field of view of the Cooperative UK T win-Located Auroral Sounding System (CUTLASS) coherent backscatter rad ar at Hankasalmi, Finland. In a recent set of experiments conducted in April 1996, the phase speed of the generated plasma irregularities ha s been compared with independent measurements of the plasma drift velo city observed by the European Incoherent Scatter radar facility. The p hase speed of the plasma irregularities is found to be equal to the co mponent of the plasma drift velocity in the direction of propagation o f the plasma wave. This result is a further verification of the high p erformance of the CUTLASS radar and also demonstrates how artificially generated plasma irregularities can be employed to detect small plasm a drift velocities and contribute to geophysical research. The charact eristics of the Doppler spectrum of the artificial plasma waves are al so described and discussed.