Variations of Sq foci position from the Indian longitudes and its influence on Equatorial Electrojet

Abstract

The latitudinal positions of the Sq focus of the northern and southern Sq loops in the Indian sector have been estimated for solar cycle-24. The Sq focus in the northern hemisphere exhibits annual variation with maximum Equatorward movement at the summer solstice and maximum poleward movement at the winter solstice. Whereas the Sq focus in the southern hemisphere exhibits semi-annual variation, with maximum Equatorward movement at the spring and autumn equinoxes and maximum poleward movement at the summer solstice (in the northern hemisphere). The seasonal variations in Equatorial Electrojet (EEJ) show a weak relationship with Sq focus movement. EEJ shows higher amplitudes for spring and autumn equinoxes when the Sq focus of both hemispheres moves towards Equator, and EEJ is weak for winter and summer solstice when either of the foci is far away from the Equator. The observed equinox asymmetry in EEJ amplitude, where EEJ shows higher amplitudes in September than March, might be due to the northern Sq focus being closer to the Equator in September compared to March. The correlation analysis shows a weak anti-correlation between daily EEJ peaks and northern Sq foci positions. A weak anti-correlation is also observed between EEJ daily peaks and the radial distance of foci. The occurrence pattern of CEJs shows a clear seasonal trend, with large numbers of CEJs for the winter and summer solstices and fewer CEJs during the equinoxes.