Simultaneous Emergence of the X‐Pattern of the Equatorial Ionization Anomaly in the American and Asian Sectors During a Geomagnetically Quiet Day

Abstract In this work, we report the simultaneous emergence of the X‐pattern of equatorial ionization anomaly (EIA) in the American and Asian sectors during a geomagnetically quiet day for the first time through the Global‐scale Observations of the Limb and Disk and Global Ionosphere Specification data assimilation products. The Ionospheric Connection Explorer (ICON) flying over the X‐pattern shows that vertical ion drift is downward around the cross and upward on both sides, along with the simultaneously observed neutral winds. The morphology of the EIA‐X is successfully reproduced by the Whole Atmosphere Community Climate Model‐Xtended with the constraint lower atmosphere (SD‐WACCMX). The mechanism behind the simultaneous EIA‐X is further clarified. We find that the EIA‐X cross coincides with the amplitude peaks of zonal neutral winds associated with the diurnal tide, and is primarily driven by downward ion drift resulting from the E‐region dynamo modulated by these zonal winds.