A coordinated experiment was conducted on March 7, 1972, in which electric fields, the mean E region neutral wind velocity, and the electron density profile were obtained in the vicinity of a radar scattering volume producing diffuse auroral echoes. The measurements were made by the Chatanika incoherent scatter radar, from the motions of barium ion clouds released by a NASA rocket. These plasma parameters were compared with the Doppler velocity maps obtained by a scanning auroral backscatter radar located at Homer, Alaska. From a threshold analysis of the data we show that the diffuse auroral echoes observed were not produced by primary plasma waves generated by the Buneman-Farley two-stream instability.