Study of OH Bands at Mt Abu, India

Abstract

The intensities of two hydroxyl bands, OH (7-2) band origin at 6861 A, and OH (8-3) band origin at 7273 A, are recorded on all clear moonless nights at Mt Abu, during the period November 1966-May 1969. Both the bands show striking similarities in their behaviour showiel1 very high positive correlation. The hydroxyl night glow exhibits different types of nocturnal variation. Continuous decay till midnight followed by an increase in intensity towards dawn is the most common type of variation. The possible, causes of the different types of variation exhibited by OH are discussed in view of the two excitation mechanisms proposed for the OH night glow, considering the possible contribution from the two reactions. It is concluded that ozone-hydrogen mechanism is the main reaction as far, as nocturnal variation is concerned. The OH night glow shows maximum intensity in winter months and minimum intensity in April. This variation is more or less opposite to that of 5577 A radiation. There is an apparent increase of OH intensity with solar activity, the intensity being more in the high active period. The OH intensity also increases following magnetic storms.