Generation of small-scale irregularities in the equatorial electrojet

A theory that accounts for the generation of short-wavelength irregularities in the equatorial electrojet for an electron drift velocity below the ion-acoustic speed is presented. Long-wavelength (tens of meters) horizontally propagating waves driven unstable by the ambient ionization density gradient are found not to steepen very much, even though they are nondispersive. However, the local vertical velocity and horizontal density gradient associated with these waves are capable of generating the meter-wavelength obliquely propagating irregularities detected in radar observations.