Solar cycle effects on the electric fields in the equatorial ionosphere

Abstract

The horizontal east-west electric fields in the equatorial F region are estimated by using the vertical electron drift data over Jicamarca, Peru. The reversal of the electric field from west to east near the sunrise hours is not affected by solar cycle, but the evening reversal is found to occur about 1 hour earlier during low-sunspot years. The average value of the electric field magnitude during noon hours is the same for different portions of the solar cycle; however, the day to day variation is larger during years of low solar activity. The postsunset increase of the electric field is characteristic of high-sunspot periods only. Abnormal reversals of the electric field are seen on some occasions during the daytime hours, and these events are associated with the equatorial counter electrojets.