Abstract
Abstract. Simultaneous observations of OI 777.4 and OI 630.0 nm nightglow emissions were carried at a low-latitude station, Allahabad (25.5° N, 81.9° E; geomag. lat. ∼ 16.30° N), located near the crest of the Appleton anomaly in India during September–December 2009. This report attempts to study 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, the electron density maximum (Nm) and its height (hmF2) of the F layer have been derived from the information of two calibrated intensities. Nocturnal variation of Nm showed the signatures of the retreat of the equatorial ionization anomaly (EIA) and the midnight temperature maximum (MTM) phenomenon that are usually observed in the equatorial and low-latitude ionosphere. Signatures of gravity waves with time periods 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 ionospheric processes.
Highlights
Ground-based airglow observations have been successfully used to derive physical parameters of the emitting region
Nocturnal variation of Nm showed the signatures of the retreat of the equatorial ionization anomaly (EIA) and the midnight temperature maximum (MTM) phenomenon that are usually observed in the equatorial and lowlatitude ionosphere
This study is an attempt to investigate the behaviour of the F region from an airglow perspective
Summary
Ground-based airglow observations have been successfully used to derive physical parameters of the emitting region. Theoretical foundation for deriving the electron density and corresponding peak using simultaneous measurements of two airglow emissions from the F region was laid by Tinsley and Bittencourt (1975). We attempt to derive Nm and hmF2 from simultaneous measurements of these two emission intensities over Allahabad (25.5◦ N, 81.9◦ E), India, on 14 nights during. Ignoring the contribution of the ion–ion recombination mechanism to OI 777.4 nm emission (Tinsley et al, 1973), its intensity (I 7774) depends upon the product of O+ ion concentration, [O+], and electron density, ne. Following expression relating the I7774/I6300 ratio with the height of the F layer (in km): hmF2 = e0.171×ln I7774/I6300 +6.43 This expression has been used to determine the height of the peak of electron density in the present study
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