In this paper we present Doppler velocity maps of the diffuse radar aurora obtained at 398 MHz with a backscatter radar located at Homer, Alaska. From the spatial distribution of Doppler velocities, we show that (1) the auroral echoes are definitely produced by scatter from wavelike fluctuations in the electron density such as those generated by a plasma instability; (2) the plasma instability is intimately associated with the electron-ion streaming velocity; (3) the Doppler velocity appears to be dependent on the magnetic aspect angle; and (4) the Doppler velocity characteristics are at least qualitatively, consistent with a quasi-linear plasma instability model developed by Sudan et al. (1973).