Observations of the F3-layer at equatorial region during 2005

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

“…Further, the foF2 just before the appearance of the F3 layer almost matches with the foF3, when the F3 layer appears, indicating that the F3 layer is not formed by the additional production of ionization, but as a result of the redistribution of ionization. The decrease in foF2 with the appearance of F3 is expected and it corroborates with the earlier results Rama Rao et al, 2005;Zain et al, 2008). …”

“…The earlier studies on the F3 layer occurrence did not distinguish between the magnetically quiet and active conditions (Lynn et al, 2000;Batista et al 2002;Rama Rao et al, 2005;Zain et al, 2008). It is observed that over Trivandrum within a particular year, the occurrence of the F3 layer is higher during the disturbed days than during the quiet days.…”

“…But, for the quiet days of the solar minimum year of 2005, the occurrence is higher during the equinox. Zain et al (2008) have reported that over the equatorial region of Malaysia during the solar minimum year of 2005, the F3 layer occurrence is more pronounced during the winter and equinoxes. Their study shows that there is an absence of the F3 layer occurrence during the summer months of May, June, July and August.…”

“…Rama Rao et al (2005) reported the ionosonde observations of the F3 layer over Waltair (17.7 • N; 83.3 • E; dip lat ∼ 8.2 • N) in India. Zain et al (2008) reported the observations of the F3 layer at the equatorial regions in Malaysia during 2005. The solar activity dependence of the F3 layer occurrence was studied by Batista et al (2002) at Fortaleza and by Rama Rao et al (2005) at Waltair, which confirmed that the layer becomes less distinct and less frequent as the solar activity increases.…”

Features of theF3layer in the low-latitude ionosphere at sunset

“…This additional layer was later renamed the F 3 layer because it has the same chemical composition as the F region . After that, the subject of the F 3 layer received extensive investigations at low and equatorial latitudes concerning its spatial and temporal distribution [Jenkins et al, 1997;Balan et al, 1998;Hsiao et al, 2001;Batista et al, 2002;Rama Rao et al, 2005;Zain et al, 2008;Uemoto et al, 2007;Sreeja et al, 2010;Zhao et al, 2011], and also its storm time characteristics [Zhao et al, 2005;Paznukhov et al, 2007;Balan et al, 2008;Sreeja et al, 2009;Zong et al, 2010]. The mechanism of the storm time F 3 layer resembles that in quiet periods and was caused by a rapid upward E × B drift resulting from an eastward penetration electric field but sometimes can be caused by strong field-aligned diffusion due to the storm time meridional wind surges as proposed by Lin et al [2009aLin et al [ , 2009b.…”