SuperDARN measurements of double-peaked velocity spectra
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The SuperDARN HF radars in Saskatoon, Sask. and Kapuskasing, Ont. have been used to measure Doppler velocity spectra of backscatter from the F-layer. A special multi pulse sequence was developed to increase the number of measured autocovariance points. These spectra were used to benchmark spectral estimators based on the Fourier Transform and parametric spectral estimators. A parametric spectral estimator using the Burg algorithm improved the resolution of the spectra. A distinct double-peaked spectral signature was found in spatially localized regions. A comparison with particle data as measured by a DMSP satellite suggests a strong spatial correlation of soft-electron precipitation with great variability with the occurrence of the spectral features. Several generating mechanisms for double-peak spectra are suggested, including the Kelvin-Helmholtz instability and precipitation-induced electric fields in arc and ray structures.