Morphological characteristics of equatorial ionization anomaly crest over nanning region

Using the ionospheric total electron content (TEC) and the location of the equatorial ionization anomaly (EIA) crest derived from GPS data observed at Nanning (22.84°N, 108.33°E, dip latitude ∼ 12.14°N), China, a GPS station situated near the daytime EIA crest region, the local time, seasonal, and solar cycle variations of EIA crests from 2006 to 2015 was investigated. The TEC and the magnetic latitude (MLAT) location of EIA crest experience an ascendant and descendant process with the daytime evolution of EIA crest. Also, this diurnal variation of EIA crest depends on season and solar cycle. The TEC and MLAT location of EIA crest is stronger and higher in equinoctial months than that in solistial months showing a semiannual variation. The TEC and MLAT location of EIA crest increase with the solar activity. The local time, seasonal, and solar cycle variations of EIA crest is consistent with that of the strength of equatorial electrojet (EEJ). Comparatively, the correlation of the EEJ strength with the EIA location is better than that with the TEC of EIA crest.