VHF power spectra of the radar aurora

Power spectra of VHF radar auroral echoes were obtained near Anchorage, Alaska, during October 15–23, 1970. These spectra were obtained concurrently with standard range-time-intensity (RTI) film strips of the echoing region using the same radar system. In this paper, these spectra and the RTI film strips are examined and are compared with previously defined radar auroral classifications. The results indicate that there are at least two, and possibly three, separate types of spectra that correspond to identifiable echo configurations on the RTI film strips. Identification of the two-stream instability as an irregularity-producing mechanism for one of these spectral types is possible but not definitive. Another type of spectrum is similar to the type II spectra seen in the equatorial electrojet. The third spectral type bears no similarity to any results obtained at the equator.