Midlatitude observations of the night airglow: Implications to quenching near the mesopause

Midlatitude observations of the night airglow from 3000 to 9200 Å were made with a ground‐based panchromatic intensified charge coupled device (ICCD) spectrograph over a period of 4 months. Intensities of the Herzberg I, Chamberlain, Herzberg II, and atmospheric systems of molecular oxygen, the Meinel bands of hydroxyl, and the atomic oxygen 5577‐Å emission were measured. Synthetic spectra and integration were used to determine the emission intensities of these features. The results were used to constrain a middle atmospheric model. Output from this model showed that quenching processes severely depopulate the states to the extent that electronic, vibrational, and rotational populations do not retain the signatures of the excitation reactions or the radiative depopulation processes. The observed coupling between the levels of the O 2 ( A ³Σ u + , A ′ 3 Δ u , c 1 Σ u − ) states and the observed vibrational distribution of the OH( X 2 II) levels also supported this heavy quenching hypothesis. The average intensities for a 6.5‐hour integration period on March 16, 1991, of the O 2 Herzberg I, Chamberlain, Herzberg II, and atmospheric (0‐1) emissions were 350±30 R, 120±15 R, <120 R, 350±20 R, respectively; the OH Meinel (9‐4), (8‐3), (7‐2), (7‐3), (6‐2), (5‐1), and (4‐0) intensities were 450±50 R 450±20 R, 90±20 R, 1620±200 R, 970±50 R, 680±150 R, 190±20 R; the O I(5577 Å) intensity was 320±10 R; the average OH Meinel (6‐2) temperature was 200° K.