Atmospheric solar tides and their electrodynamic effects—II. The equatorial electrojet

Abstract

The global-scale dynamo solution in Part I is used to determine a full three-dimensional solution within the equatorial electrojet. Inclusion of vertical currents near the magnetic equator nearly doubles the magnetic variation obtained from the thin-shell dynamo model, relaxing the need for E-region diurnal wind speeds as large as those required by previous workers to reproduce the S q current system. This occurs because the electrojet is broadened both vertically and in its north-south extent when three-dimensional current flow is permitted. The underlying physics of this enhancement of the electrojet intensity over that predicted by the thin-shell approximation is discussed. The three-dimensional electrojet structure confirms salient features of simpler noontime meriodional-plane electrojet models, if these are extended to couple with local time variations of the polarization field generated by global dynamo action. By including local winds in our electrojet model, we are able to simulate the double-peaked structures observed near the magnetic equator by rocket-borne magnetometers. The model is also utilized as an aid in elucidating other electrojet phenomena, including the occurrence of plasma instabilities and the counter-electrojet.