Morphological Differences of the Northern Equatorial Ionization Anomaly Between the Eastern Asian and American Sectors

The morphological difference of the northern equatorial ionization anomaly between the eastern Asian and American sectors is statistically studied with ground‐based total electron content data from 2000 to 2011. The intensity ( Ic ), latitudinal location ( Lc ), and occurrence time ( Tc ) of the daytime equatorial ionization anomaly crest are derived from daytime peak total electron content in time‐latitude plots. The main results are as follows. Lc in the two sectors exhibits an apparent difference, especially in solar minimum, during which Lc in the American sector shows an annual variation that is more poleward in northern summer and more equatorward in northern winter, while Lc in the eastern Asian sector shows a semiannual variation that is more poleward around equinoxes and more equatorward around solstices. Ic tends to be stronger in the eastern Asian sector than that in the American sector in all seasons, and this difference increases with the increase of the solar flux index. Tc tends to be earlier in northern winter and later in northern summer in both sectors and shows dependence on solar activity. We demonstrate that the seasonal variation of Lc in the American sector is not dominated by the ionospheric equatorial zonal electric field, and suggest that the difference of Lc between the two sectors is probably related to different meridional wind effects due to the displacement of geographic and magnetic equators. The Ic difference is probably related to the longitudinal wave number‐3 and ‐4 structures driven by tidal forcing from the 5lower atmosphere. The seasonal variation of the northern EIA crest location is distinctly different between the eastern Asian and American sectors Such difference is probably related to the different meridional wind effects due to the displacement of geographic and magnetic equators The EIA crest intensity tends to be stronger in the eastern Asian sector in all seasons that may be due to the nonmigrating tides