Intensity variations and ratios of (9-4) and (7-3) hydroxyl bands in nightglow at Poona

Abstract

The observed types of nocturnal intensity variations for the OH (9-4) and OH (7-3) bands during IQSY at this Station are further analysed using the theoretical band intensity distribution of Evans and Llewellyn (1972). A considerable agreement is noticed between observed and theoretical intensity ratios, I(9-4) I(7-3) , for a major portion of the data (∼70%), which has a “continuous decrease” type of noctural intensity variation. This data is thereby satisfactorily explained on the basis of available information. For the remaining portion of the data (∼30%), which has “an increase followed by decrease” type of intensity variation and higher intensities, the observed ratios are also systematically higher than the above. A satisfactory explanation is offered, by postulating a second layer of emission, by examining closely several aspects of the other observational results.