Equatorial Ionization Anomaly X-Pattern Occurrences Observed by the GOLD Mission During Its First 5 Years

Abstract

The Global-scale Observations of Limb and Disk (GOLD) mission has provided an unusual array of upper atmosphere observations from a geostationary platform, including the behavior of the low latitude nighttime ionosphere. One of the features observed by GOLD is the formation of an X-pattern in the Equatorial Ionization Anomaly when its crests collapse near the magnetic equator. This paper discusses the X-patterns that were observed during the first 5 years of the GOLD mission (2018–2023). This catalog reveals that X-pattern occurrences are more frequent during low solar activity, and appear to be driven by changes in the normal low latitude zonal winds. In the longitude region observed by GOLD (approximately 75°W–5°E) they occurred exclusively during the September Equinox-December Solstice-March Equinox seasons, and they were more likely to occur near 45°W longitude, near the point where the geomagnetic equator crosses the geographic equator in the western hemisphere.