A comparative study of the northern and southern equatorial ionization anomaly crests in the East-Asian sector during 2006–2015

Abstract

The GPS observation data measured at GXUN (22.84°N, 108.33°E, MLAT ~ 12.14°N) and BAKO (6.49°S, 106.84°E, MLAT ~ 17.18°S) stations from 2006 to 2015 are utilized to make a comparative study of the northern and southern equatorial ionization anomaly (EIA) crests in the East-Asian sector. The intensity of northern EIA crest is similar to that of southern EIA crest during the solar minimum years, while during the solar maximum years, the intensity of northern EIA crest is a little stronger than that of southern EIA crest except in summer season of northern hemisphere. The geomagnetic latitude (MLAT) of northern EIA crest shows a weak semiannual variation with the highest in equinoctial months and the lowest in solistical months, but the MLAT of southern EIA crest shows a clear annual variation with the highest in summer season of southern hemisphere and the lowest in winter season of southern hemisphere, which is particularly obvious during the solar minimum years. The intensities of northern and southern EIA crests have good correlation, which is independent of the solar activity, but the correlation coefficients of MLAT between northern and southern EIA crests increase with the solar activity. A comprehensive analysis of the previous studies and our results indicate that the intensity, MLAT, and interhemispheric asymmetry of EIA crest are mainly dominated by photochemical process, equatorial fountain effect, and neutral wind, respectively.