On the development of nonlinear waves in the equatorial electrojet

Theories for the equatorial electrojet (EEJ) have been notoriously difficult to resolve with data. Two of these problems were solved recently and another is discussed in this publication. We initially review solutions to the first two issues: the constant phase velocity of 3 m waves in the EEJ with zenith angle and the disagreement between the observed and calculated altitude of the EEJ current. One remaining problem is the nonlinear nature of large-scale waves in the electrojet that appear as square waves. One possibility is the conversion of free energy into ion acoustic waves, which limits the large-scale wave amplitude to the threshold for producing such waves. Another is the breaking of large-scale waves when the perturbation velocity internal to the wave approaches the wave phase velocity. (C) 2013 Published by Elsevier Ltd.