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Doppler spectra of the UHF diffuse radio aurora

1988; American Geophysical Union; Volume: 93; Issue: A7 Linguagem: Inglês

10.1029/ja093ia07p07425

2156-2202

G. Emlen Hall, D. R. Moorcroft,

Solar and Space Plasma Dynamics

A large number of radar backscatter Doppler spectra from the 398‐MHz phased array at Homer, Alaska, have been analyzed for representative periods of widespread, long‐lasting radar echoes in the premidnight and postmidnight sectors. Spectra corresponding to type 1 and type 2 echoes were observed. The type 1 spectra were most evident in the postmidnight data, where they appeared as velocity plateaus in azimuthal scans at the farther ranges. The type 2, low‐velocity spectra were generally observed only in the absence of type 1 echoes. The spectral widths of the type 2 spectra were consistent with decay rates estimated by linear theory, as might be expected for dissipative waves at the short‐wavelength end of a turbulent cascade. The velocity plateaus and other features of the azimuthal and range variation of Doppler velocity can be understood if the auroral electrojet is assumed to have moderate variations in direction on a scale of tens of kilometers. It was possible to obtain from the Doppler data qualitative estimates of the electric field, whose variation in time and latitude was in general agreement with the model electrojet configuration of Kamide and Vickrey (1983).