Statistical study of high-latitude E-region Doppler spectra obtained with the SHERPA HF radar

摘要: A large number of Doppler spectra obtained at six HF frequencies in the E region with SHERPA radar are analyzed statistically. They characterized by their total power, mean velocity and spectral width. The observations cover geomagnetic conditions varying from quiet to disturbed. Due location auroral oval relative field view, echoes preferentially detected morning westward electrojet, radial velocities away radar. This results an asymmetrical distribution. Both usual Type 1 2 spectra, associated two-stream gradient-drift waves, respectively, origin two peaks Other types do not appear statistics. Spectral widths remain narrow for both types. is explained a longer lifetime wave trains compared higher frequency waves VHF radars. decrease related gradient effects on threshold, as predicted linear dispersion equation instability