Sporadic Structures in the Equatorial Ionosphere from the GPS—Formosat-3 Radio-Occultation Experiments

We analyze the results of the radio-occultation experiments which were carried out for six years in two equatorial regions of the lower ionosphere. The features of the decimeter radio-wave amplitude variations are considered for the case of remote sensing of the different sporadic structures along the radio paths between two satellites. The diurnal dependences of the height and thickness of the Es layer are presented for different time intervals. It is shown that in different days in the nighttime the Es-layer plasma structures can exist in the form of a single layer or in the form of two layers simultaneously. The first layer is located at an average altitude of 116 km, while the second one, at 96 km. It was found that in the daytime the height of the first layer decreases, while in the evening, irregular structures are formed at altitudes distributed randomly between 90 and 100 km. The amplitude variations of the sounding signals are discussed for cases where the distance (in the perigee) of the radio ray path from the Earth’s surface is between 70 and 85 km in the mesosphere. Statistics of the sporadic structure occurrence is given for the regions located in Africa and Indonesia.