The equatorial electrojet

An integrated treatment of observations and models of the undisturbed equatorial electrojet is presented. Previous reviews have concentrated on particular aspects of the electrojet phenomenon, such as ground magnetic variations, the counterelectrojet, or E region electron density irregularities and associated plasma instabilities. Here accomplishments during the past 15 years involving all aspects of the phenomenon are covered and, where possible, interrelated. Observational and theoretical studies during recent years have emphasized the local time, longitude, vertical, and latitudinal structure of electric fields and currents in the electrojet; this review similarly places its emphasis along these lines and by necessity involves a detailed examination of electrodynamic coupling with the neutral atmosphere tidal oscillations in temperature, composition, and winds. The review concludes with an assessment of current knowledge concerning the equatorial electrojet and suggestions for the future direction of observational and theoretical research on electrodynamical processes in the equatorial ionosphere.