Propagation and dispersion of electrostatic waves in the ionospheric E region

Low-frequency electrostatic ̄uctuations in the ionospheric E region were detected by instruments on the ROSE rockets. The phase velocity and dispersion of plasma waves in the ionospheric E region are determined by band-pass ®ltering and cross-correlating data of the electric-®eld ̄uctuations detected by the probes on the ROSE F4 rocket. The results were con®rmed by a di€erent method of analysis of the same data. The results show that the waves propagate in the Hall-current direction with a velocity somewhat below the ion sound speed obtained for ionospheric conditions during the ̄ight. It is also found that the waves are dispersive, with the longest wavelengths propagating with the lowest velocity.