Spectral studies of F region irregularities in the auroral zone

Auroral F region irregularities have been studied with the HF coherent radar system SAFARI at wavelengths of 10.5 and 7.0 meters. Their Doppler spectra exhibit large spatial and temporal variations which indicate that the phase velocity is related to the motion of the bulk plasma. This observation agrees with a production by low energy precipitations or plasma instabilities like cross‐field instability or current‐convective instability. Coordinated ground‐based and satellite measurements are necessary to conclude definitely on the origin of these irregularities.