Abstract. Simultaneous observations of OI 777.4 nm and OI 630.0 nm nightglow emissions were carried at a low latitude station, Allahabad (25.5º N, 81.9º E, geomag. lat. ~16.30º N), located near the crest of Appleton anomaly in India during September–December 2009. This study attempts to examine the behaviour of the F region of ionosphere using airglow derived parameters. Using an empirical approach put forward by Makela et al. (2001), firstly, we propose a novel technique to calibrate OI 777.4 and 630.0 nm emission intensities using Constellation Observing System for Meteorology, Ionosphere, and Climate/Formosa Satellite Mission 3 (COSMIC/FORMOSAT-3) electron density profiles. Next, electron density maximum (Nm) and its height (hmF2) of the F-layer have been derived from the information of two calibrated intensities. Nightglow derived Nm and hmF2 were in reasonable agreement with few measurements reported earlier. Nm and hmF2 were used to study the behaviour of the F-region over Allahabad on the limited number of nights. Nocturnal variation of Nm showed the signatures of the retreat of equatorial ionization anomaly (EIA) and mid-night temperature maximum (MTM) phenomenon that are usually observed in the equatorial and low-latitude ionosphere. Signatures of gravity waves having period in the range of 0.7–3.0 h were also seen in Nm and hmF2 variations. Sample Nm and hmF2 maps have also been generated to show the usefulness of this technique in studying the ionospheric processes.
Origin and Distribution of Daytime Electron Density Irregularities in the Low‐Latitude
F
Region