Height and latitude structure of electric fields and currents due to local east‐west winds in the equatorial electrojet

Abstract

Using the equivalent electrical circuit method for the theoretical treatment of the local wind effects on the equatorial electrojet, the height structures of electric fields and currents that are generated by height‐varying east‐west winds in the electrojet region have been calculated for theoretical model wind sturctures and for a variety of experimentally observed wind structures. The results bring out clearly the nature and extent of the local wind effects on the height and latitude structures of the equatorial electrojet.The more important conclusions of the present study are: (a) The vertical wind shears associated with tidal winds and gravity waves can generate significantly large electric fields and east‐west currents in the equatorial electrojet (EEJ). (b) The wind‐generated electric fields and currents are characterized by large height gradients, latitudinal gradients, and reversals of direction. (c) At the magnetic equator, wind‐generated electric fields and currents are often small (10%–30%) in comparison with the eastward electric‐field‐generated polarization field and east‐west currents around noon hours. (d) At geomagnetic latitudes of 3° and beyond the wind‐generated currents and electric fields often exceed those caused by the eastward electric field. (e) Beyond 2° the neutral winds can drastically alter the intensity and latitudinal structure of the EEJ, depending upon the magnitude and height location of the wind shear. (f) The observed variabilities in the ‘width’ and latitude structure of the EEJ can arise from the effects of such east‐west winds that have been observed experimentally.