Role of gravity wave like seed perturbations on the triggering of ESF - a case study from unique dayglow observation

Abstract

First observational evidence, from the Indian longitudes, for the presence of gravity wavelike perturbations with periods of 20-30 min, acting as probable seeds for Equatorial Spread F (ESF) irregularities is described. The study is based on the daytime optical measurements of the mesopause temperature and the intensity of the thermospheric O(¹D) 630.0 nm dayglow emissions using the unique MultiWavelength Dayglow PhotoMeter from Trivandrum (8.5° N; 77° E; dip lat ˜0.5° N), a dip equatorial station. Measurements during the equinoctial months of a solar maximum (2001) and a solar minimum year (2006) have been used in this study. It is shown that under identical background ionospheric conditions within a solar epoch, the power of the gravity waves have a deterministic role in the generation of ESF. The mesopause temperature simultaneously observed, indicate that possible source regions for these perturbations lie in the lower atmosphere.