Longitude and Seasonal Variations of the <i>S</i>_<i>q</i> Current System

Abstract

The ‘equivalent circuit method’ of deriving electric currents in the ionosphere from assumed values of conductivities and emf's has been described earlier. The ionosphere is represented as a large circuit network, with the Hall effect included, and this network is solved by an iterative procedure on a computer. A single tidal wind system, the ‘1—2’ mode, is used as the driving force of the dynamo. The winds are converted from the geographic to the geomagnetic coordinate system. The international geomagnetic reference field (IGRF) is used to provide magnetic field values for calculating the dynamo emf's and the conductivities. The agreement between the calculated and observed positions of the focuses of the current system is remarkable when we consider that no seasonal variation of the wind was included. Seasonal variations of the reversal times of the equatorial electrojet are obtained in rough agreement with observation, whereas the calculated variations of the intensity of the electrojet do not agree so well.