Morphology of sporadic <i>E</i> layer retrieved from COSMIC GPS radio occultation measurements: Wind shear theory examination

<jats:title>Abstract</jats:title><jats:p>On the basis of the Constellation Observing System for Meteorology, Ionosphere, and Climate (COSMIC)‐measured fluctuations in the signal‐to‐noise ratio and excess phase of the GPS signal piercing through ionospheric sporadic <jats:italic>E</jats:italic> (<jats:italic>E</jats:italic>s) layers, the general morphologies of these layers are presented for the period from July 2006 to May 2011. It is found that the latitudinal variation in the <jats:italic>E</jats:italic>s layer occurrence is substantially geomagnetically controlled, most frequent in the summer hemisphere within the geomagnetic latitude region between 10° and 70° and very rare in the geomagnetic equatorial zone. Model simulations show that the summer maximum (winter minimum) in the <jats:italic>E</jats:italic>s layer occurrence is very likely attributed to the convergence of the Fe<jats:sup>+</jats:sup> concentration flux driven by the neutral wind. In addition to seasonal and spatial distributions, the height‐time variations in the <jats:italic>E</jats:italic>s layer occurrence in the midlatitude (>30°) region in summer and spring are primarily dominated by the semidiurnal tides, which start to appear at local time around 6 and 18 h in the height range 110–120 km and gradually descend at a rate of about 0.9–1.6 km/h. In the low‐latitude (<30°) region, the diurnal tide dominates. The Horizontal Wind Model (HWM07) indicates that the height‐time distribution of <jats:italic>E</jats:italic>s layers at middle latitude (30°–60°) is highly coincident with the zonal neutral wind shear. However, <jats:italic>E</jats:italic>s layer occurrences in low‐latitude and equatorial regions do not correlate well with the zonal wind shear.</jats:p>