Ionospheric electron content within the equatorial F₂ layer anomaly belt

Abstract

This paper describes some new results on the day-to-day behavior of the location of the equatorial anomaly in the columnar electron content. The measurements were made from a unique network of stations covering dip latitudes from 0°N to 25°N during the period in 1975-1976 near sunspot minimum when the ATS 6 satellite was visible from India. The latitudinal distribution of the total electron content on a particular day was found to depend only on the strength of the electrojet current, as determined by the difference of the horizontal magnetic field at stations on the magnetic equator and another outside the equatorial electrojet, rather than on the horizontal magnetic field measured only at the equatorial station. During magnetically disturbed periods the presence or absence of the anomaly was also found to depend only upon the strength of the electrojet current. The varying electrojet current, that is, the equatorial electric field, is very effective in moving the ionization to the anomaly latitudes of 15°-20°, but the columnar electron content over the magnetic equator remains relatively constant.