Motions of the equatorial ionization anomaly crests imaged by FORMOSAT‐3/COSMIC

The equatorial ionization anomaly (EIA) structures and evolutions are imaged using radio occultation observation of the newly launched FORMOSAT‐3/COSMIC (F3/C) satellite constellation. Three‐dimensional ionospheric images provide unprecedented detail of the EIA structure globally. This paper presents images of the EIA structures during July–August 2006 and discusses the development and subsidence of the EIA. Clear seasonal asymmetries in both ionospheric electron density and layer height are observed. Two‐dimensional (cross section) maps at a meridian provide dynamic variations and motions of the northern and southern EIA crests. Results suggest that in addition to the asymmetric neutral composition effect, interactions between the summer‐to‐winter (transequatorial) neutral winds and strength of the equatorial plasma fountain effect play important roles in producing asymmetric development of the EIA crests as imaged by the F3/C.