A simulation study on the semiannual variation of the ionospheric F 2 layer zonal electric fields at the magnetic equator

Abstract

With a theoretical model which yields ionospheric electric fields, we study the yearly variation of ionospheric electric fields at middle and low latitudes under the condition of low solar and quiet geomagnetic activities. The results show the following characteristics. When the ionospheric electric fields are calculated individually in the Northern (or Southern) Hemisphere without including the influence of the other hemisphere (uncoupled), the electric field in the Northern (or Southern) Hemisphere varies in an obvious annual pattern; when the electric field is calculated simultaneously in both .hemispheres including the influence of the other hemispheres (coupled), the electric field varies in a predominantly semiannual pattern. Moreover, quite good consistency was found between the behaviors of semiannual variation calculated by our theoretical electric field model and an empirical model of Richmond et al. (1980). Copyright 2006 by the American Geophysical Union.