Local time dependence of the equatorial counter electrojet effect in a narrow longitudinal belt

Abstract

Irregular occurrence characteristics of the equatorial counter electrojet phenomena at different longitudinal zones are investigated using the magnetic data of the horizontal component ‘H’ at the two equatorial stations Trivandrum and Addis Ababa, separated in longitude by about 40°. The limited longitudinal extent of the counter electrojet (CEJ) events are examined on the basis of the occurrence of the phenomenon at different local time intervals. Importance of the solar semi diurnal tides in modifying the equatorial counter electrojet phenomena at Trivandrum and Addis Ababa is discussed during these local time groups. Dominance of semi-diurnal tidal modes of varying magnitude is found to influence the local time occurrence behaviour of CEJ events over the equator. Peculiarities of both the change in amplitude and phase pattern of the diurnal variation of the ‘H’ component within the narrow longitude sector, especially during the noon hours, indicate the modulation of the diurnal variation of the equatorial electrojet currents by vertical wind shears of highly localised nature