GOLD Observations of Longitudinal Variations in the Nighttime Equatorial Ionization Anomaly (EIA) Crests' Latitudes

Each day the Global-scale Observations of the Limb and Disk imager observes the equatorial ionization anomaly (EIA) near sunset from similar to 10 degrees E to similar to 80 degrees W geographic longitude. Most images cover similar to 45 degrees of longitude (similar to 3 hr), and most longitudes are observed multiple times. Monthly averages of EIA crests' latitude (EIA lats) versus longitude during March, September, and December 2020 have been analyzed. The EIA lats reflect the combined influence of winds, solar radiation, and fields (electric and magnetic) in the equatorial region. Winter solstice differs significantly from the equinoxes, which are similar, but there are notable similarities between all three. The similarities in the EIA lats during the seasons examined indicates that the magnetic equator to subsolar point separation influences them in all three seasons and that it has a more distinct, possibly more significant, influence than winds on the average latitudes.Plain Language Summary Each day the Global-scale Observations of the Limb and Disk imager observes the nighttime equatorial ionization anomaly (EIA) near sunset as the terminator progresses westward from Africa to across South America. Most images cover similar to 45 degrees of longitude (similar to 3 hr of local time), and most longitudes are observed multiple times. In 2020 seasonal averages of the crests' latitude versus longitude during the equinoxes (March and September) and winter solstice (December) show significant, important similarities. The observed latitude versus longitude dependence in all three show a dependence on the distance between the magnetic equator and the subsolar point. Greater knowledge of the seasonal-longitudinal dependence of the EIA crests' latitudes contributes significantly to understanding the crests' response to fields (electric and magnetic) and winds in the equatorial region. Plain Language Summary Each day the Global-scale Observations of the Limb and Disk imager observes the nighttime equatorial ionization anomaly (EIA) near sunset as the terminator progresses westward from Africa to across South America. Most images cover similar to 45 degrees of longitude (similar to 3 hr of local time), and most longitudes are observed multiple times. In 2020 seasonal averages of the crests' latitude versus longitude during the equinoxes (March and September) and winter solstice (December) show significant, important similarities. The observed latitude versus longitude dependence in all three show a dependence on the distance between the magnetic equator and the subsolar point. Greater knowledge of the seasonal-longitudinal dependence of the EIA crests' latitudes contributes significantly to understanding the crests' response to fields (electric and magnetic) and winds in the equatorial region.