The capability of Stare (Scandinavian twin auroral radar experiment) to perform cross beam measurements over a large area in the E region, is used to study prominent Doppler spectrum features of 140 MHz auroal backscatter. By analyzing an extended spectral data base, two less common but distinct spectrum types were identified, in addition to the well known and commonly observed type 1 and type 2 spectra. The evidence shows that, at times, meter scale irregularities may propagate with preferential phase velocities not only near but also below and above the ion acoustic speed always inside well defined ranges from 150 to 250 m/s and from 900 to 1200 m/s, respectively. The new 140 MHz phase velocity values compare well with similar values reported previously with 50 MHz radars; this supports the notion of characteristic plasma wave phase velocities and not that of characteristic angular frequencies as it is for electrostatic ion cyclotron waves. These results are indicative of new plasma precesses in the auroral E region that need to be analytically developed and understood. ¿ American Geophysical Union 1989 |