Statistical analysis of the ionization ledge in the equatorial ionosphere observed from topside sounder satellites

Stratification of the Low-Latitude and Near-EquatorialF2Layer, Topside Ionization Ledge, andF3Layer: What We Know about This? A Review

“…Uemoto et al [49,50] reported that the ledges observed in the noontime period are qualitatively similar to the F3 layer predictions by Balan and Bailey [32], and the ledge tends to move upward during morning-noon period. Below we will use both terms (the ledge and F3 layer) believing that we are dealing with the same physical phenomenon-a stratification of the equatorial F2 layer.…”

Features of theF3layer in the low-latitude ionosphere at sunset

“…The simultaneous occurrence of the ledges in latitude TEC variation and F 3 layer in the ground ionograms suggests that topside ledges are upward propagating F 3 layers. A potential relationship between the topside ledge and bottomside F 3 layer was also pointed out by Uemoto et al [2006] who analyzed the topside ionograms of 19 and 430 passages obtained from the Ohzora and ISIS II satellites. They also found that the topside ledges can appear from the evening to slightly after midnight and occur mostly in equinox.…”

“…The topside ledge should undergo a downward drift at night. However, the results of Uemoto et al [2006] show that the altitude variations of the ionization ledge were largely scattered. The study by Yizengaw et al [2009] may provide a clue in understanding the above inconsistency.…”

“…Uemoto et al [2004Uemoto et al [ , 2006 performed a statistical analysis of the topside ledges in the equatorial ionosphere using the Ohzora (EXOS-C) and ISIS II satellite. They concluded that the characteristics of the F 3 layer and topside ledges are similar, except for the seasonal dependence of the occurrence probabilities.…”

Features of the F3 layer occurrence over the equatorial location of Trivandrum

“…Thampi et al (2005) were the first to show that the F3 layer and the topside ledges could be observed in the latitudinal profiles of Total Electron Content (TEC) measured by the low earth orbiting satellites. Using the Ohzora (EXOS-C) and ISIS-II satellite, Uemoto et al (2004Uemoto et al ( , 2006 presented a statistical analysis of the topside ledges in the equatorial ionosphere and concluded that except for the seasonal difference in the occurrence probability, the characteristics of the F3 layer and the topside ledges are similar. Based on the average upward drift (Fejer et al, 1991) and the Horizontal Wind Model (HWM) (Hedin et al, 1991), a distinct F3 layer was predicted to occur on the summer side of the geomagnetic equator (Balan et al, 1998).…”