Experimental evidence of gravity waves at 80-90 km altitude from OH night airglow observations

Abstract

Measurements of intensities at two fixed wavelengths in the OH (7-2) band were carried out at Mt Abu (24.6° N, 76.7° E) from 1973-76 to estimate neutral temperature in the region of 80-90 km altitude. It was observed that on some nights the temperature in this region shows periodic oscillations throughout the night. It was found from statistical analysis that the periods of these fluctuations are comparable to the theoretically predicted periods of internal gravity waves. If the periodic temperature variations observed in this region are attributed to the influence of gravity waves, according to the Hines theory only the magnitude of the horizontal component of wave-induced wind velocity can be computed. Using the measured relative temperature fluctuations it is found that the magnitude is 15-30 m/sec.