Features of the F3 layer in the low-latitude ionosphere at sunset

According to Balan et al. (1998) the F₃ layer occurs mainly during the morning-noon period due to the combined effect of the upward E × B drift and the neutral wind that provides upward plasma drifts at and above the F₂ layer. The F₃ layer occurrence rate is higher in summer and decreases with increasing solar activity.

In this study, the characteristic of the sunset F₃ layer is first investigated using a solar cycle of ionosonde data (1995 - 2010) from the magnetic equatorial station at Jicamarca, and compared with the features derived from the four subtropical stations at Sao Luis, Fortaleza, Kwajalein, and Vanimo. Evidence shows that the local time distribution of the occurrence of the F₃ layer can extend to the postsunset time (1800 - 2100 local time).