In two previous papers, I suggested that the electrical conductivity in E-W direction of the E region in a narrow belt along the magnetic equator is much greater than in the other latitudes, on account of a polarization field produced by the Hall Current, provided that λ is much less than 10. And that this high conductivity will cause enhanced diurnal magnetic variations near the magnetic equator.
In this paper, I discuss this theory further in detail. A dynamo theory for the E region with anisotropic conductivity, which is linked by highly conductive lines of magnetic force to the F region, is examined. A case that the E layer only makes a tidal oscillation, which produces observed lunar diurnal current system, is calculated. It is found that, in middle latitudes, the induced polarization field in E-W direction by the Hall Current is greater than that by the direct current, and the vertical drift of the F2 layer by this polarization field seems to be adequate for the observed F2 lunar variation. According to the present theory, conductivity of the E region at the magnetic equator decreases with increase of the main magnetic field, and the distribution of range of magnetic variations along the magnetic equator reported by Egedal, seems to support this relation.