Statistical Properties of Equatorial Ionospheric Anomaly Single Crests Derived from Global Ionospheric Maps

The classical Equatorial Ionization Anomaly (EIA) is characterized by two separated plasma accumulation regions off the geomagnetic equator and a plasma depletion region in-between. The strength of the equatorial plasma fountain varies longitudinally and temporally due to external driving, leading to the variable morphology of the EIA structure. Substantial deviations from the classical double-crest picture can occur. In particular, observations of single crests have been reported, yet the formation and variability of single crests are not well understood. This study focuses on the Total Electron Content single crests extracted from Global Ionosphere Maps that cover two decades. We investigate the occurrence of the single crests as well as its dependency on solar cycles, seasons, and geomagnetic activities. The variability of the latitudinal locations of the single crests are analyzed. For single crests that last for at least an hour, we track the crest trajectories to find out the motion of the crests over time. Our study contributes to the characterization and understanding the EIA single-crest phenomenon.