Zonal metal ion transport’s contribution to sporadic E layer occurrence in the austral summer southern hemisphere

Abstract We investigate the cause of the spatial distribution of sporadic E (Es) layer occurrences in the austral summer Southern Hemisphere using a numerical model that incorporates metal ion dynamics. Previous studies have attributed longitudinal variations in Es occurrence (EsO) distributions to geomagnetic field distributions, particularly suggesting that high magnetic inclination causes a significant reduction in EsO near Southern Africa. In this study, we perform Es layer simulations for low and middle latitudes in the austral summer Southern Hemisphere with and without the longitudinal variation in geomagnetic fields. We define Es occurrence rates (EsORs) on the basis of the simulation output. Our simulations successfully reproduced some features of the longitudinal variations in EsORs observed in many previous studies. The simulations showed that the longitudinal variations in EsORs are not solely determined by the geomagnetic field distribution, but also affected by the background metal ion distribution. We find that superimposed nonmigrating diurnal tides are amplified near Southern Africa between 95 and 110 km altitudes, potentially dispersing metal ions and suppressing EsO in that region. This is the first study to demonstrate that wind-driven zonal metal ion transport plays a key role in shaping EsO distributions in the austral summer Southern Hemisphere, in addition to the geomagnetic field distribution effects. Graphical Abstract