Recent work with the STARE (Scandinavian Twin Auroral Radar Experiment) and SABRE (Sweden and Britain Radar Experiment) data sets has shown some inconsistency with existing theories (fluid and kinetic theory) of radar aurora. A new technique, which we call the superimposed grid point method, has proven to be a very valuable tool in the study of this inconsistency. This technique can be used under conditions where the electron drift velocity is approximately constant over an entire STARE (or SABRE) latitude interval and consists of superimposing all of the observed radial Doppler velocity components for the entire latitude interval together into one grid point. This yields, for a given electron drift velocity, a set of Doppler velocity vectors for typically more than 30 different flow angles. Thus this technique allows the study of the angular variation of the Doppler velocities observed with the radars, for a given electron drift velocity. One of the main results of using this technique has been strong evidence that very often the radar Doppler velocities are limited to near the ion acoustic velocity in a manner very similar to the equatorial electrojet. Doppler velocities at flow angles greater than some critical flow angle appear to follow a cosine law, as is usually assumed in the fluid and kinetic theory, while velocities at flow angles less than this critical flow angle seem to deviate greatly from the cosine law and are often limited to the ion acoustic velocity.

We have reinterpreted the radar Doppler velocity measurements in the ion acoustic approach (Nielsen and Schlegel, 1985) and find consistency between the results of the superimposed grid point analysis and this new approach.