North-south components of the annual asymmetry in the ionosphere

Abstract

A retrospective study of the asymmetry in the ionosphere during the solstices is made using the different geospace parameters in the North and South magnetic hemispheres. Data of total electron content (TEC) and global electron content (GEC) produced from global ionospheric maps, GIM-TEC for 1999–2013, the ionospheric electron content (IEC) measured by TOPEX-Jason 1 and 2 satellites for 2001–2012, the F2 layer critical frequency and peak height measured on board ISIS 1, ISIS 2, and IK19 satellites during 1969–1982, and the earthquakes M5+ occurrences for 1999–2013 are analyzed. Annual asymmetry is observed with GEC and IEC for the years of observation with asymmetry index, AI, showing January > July excess from 0.02 to 0.25. The coincident pattern of January-to-July asymmetry ratio of TEC and IEC colocated along the magnetic longitude sector of 270° ± 5°E in the Pacific Ocean is obtained varying with local time and magnetic latitude. The sea/land differences in the F2 layer peak electron density, NmF2, and the peak height, hmF2, gathered with topside sounding data exhibit tilted ionosphere along the seashores with denser electron population at greater peak heights over the sea. The topside peak electron density NmF2, TEC, IEC, and the hemisphere part of GEC are dominant in the South hemisphere which resembles the pattern for seismic activity with dominant earthquake occurrence in the South magnetic hemisphere. Though the study is made for the hemispheric and annual asymmetry during solstices in the ionosphere, the conclusions seem valid for other aspects of seismic-ionospheric associations with tectonic plate boundaries representing zones of enhanced risk for space weather.