Evening and morning twilight enhancement of λ5577 A atomic oxygen line at Allahabad

A photometer for the observation of twilight airglow emissions has been fabricated. Intensity variation in morning and evening twilight of λ5577 A line of atomic oxygen has been recorded at Allahabad for one year duration from 23rd March, 1987 to 22nd March, 1988. The enhancement in the intensity of the line is found to be irregular. Out of 40 clear evenings and 25 clear mornings from 23rd March, 1987 to 15th June, 1987 enhancement is observed in 24 evenings and 15 mornings. However, no enhancement is observed during the period from 15th September, 1987 to 15th October, 1987. It is found that rise and fall of intensity is exponential during twilight period. Considering different mechanisms for the excitation of atomic oxygen green line, it is concluded that none of them are able to explain enhancement. More work is needed to better understand the problem. 15 refs.; 11 figs.; 2 tabs