Lunar tidal variations in the equatorial electrojet current

Abstract

The lunar semidiurnal variations in the solar diurnal range of the horizontal component of the earth's magnetic field H are computed for the equatorial stations that were operating in Peru during the IGY and IGC. The amplitude is found to be greatly enhanced on either side of the magnetic equator within magnetic dip of about ±10°. The narrow regions of enhanced lunar tidal effect and solar diurnal variation in H are similar to each other, suggesting that lunar semidiurnal tides affect the same region as that which contains the well-known solar diurnal equatorial electrojet. The lunar effects in South America are found to be maximum during the southern solstice at stations within the zone of the equatorial electrojet, but during the equinoxes at stations in middle latitudes.