Stratification of the Low-Latitude and Near-Equatorial F2 Layer, Topside Ionization Ledge, and F3 Layer: What We Know about This? A Review

Figure 21

Sketch of diurnal variations of the electron density profile near the geomagnetic equator: (1) the daytime electron density profile with a one-layered pattern without F2 layer stratifications. (2) the sunset electron density profile with a two-layered pattern—the F3 layer appears due to the non-uniform in height vertical plasma drift and the F2 layer disappears due to the reduction of photoionization, at that foF3 > foF2. (3) he nighttime electron density profile with a one-layered pattern—the F3 layer occurs, the F2 layer almost disappears. (4) the morning-noon electron density profile with a two-layered pattern—the F2 layer appears due to the increase of photoionization and the F3 layer continues to occur (this could also appear in the sunset local time). (5) the afternoon electron density profile with a two-layered pattern—the foF2 continue increases due to the photoionization processes, at that foF3 becomes smaller than foF2. Further the F3 layer merges with F2 layer, and the electron density profile turns type 1.