Fourier analysis of a virtual satellite view of the NIR atmospheric emission over Europe

• Published in: Advances in space research 2003-09, Vol.32 (5), p.843-848
• Main Authors: Faivrel, M., Moreels, G., Pautet, D., Clairemidi, J.
• Format: Article
• Language: English
• ISSN: 0273-1177; 1879-1948
• DOI: 10.1016/S0273-1177(03)00593-3

Observations of wave-driven fluctuations in the near-infrared nightglow at the mesopause level were performed using a CCD camera located at Châteaurenard (44°41′ N, 6°54′E) in the French Alps. In this paper, a few examples of panoramas and top circular views of the emissive layer during summer show wave fields with wide arches and stripes extending from a point in the E-SE to the diameter opposite W-NW point. The direction of the wave field is retrieved by using specific image processing techniques which mainly consist of enhancing the wave front contrast. The emission is mainly due to the OH radical; its intensity varies during the night by as much as 50% due to photochemical and tidal effects. In addition, the intensity shows smaller fluctuations induced by the propagation of wave systems. Spectral Fourier Analysis was applied to the intensity spectra in order to retrieve the wavelengths and temporal periods of the waves travelling through the emissive layer at the altitude of 88 km. The measured wavelengths range from 25 to 69 km. The apparent periods range from 10 to 40 minutes. As a result, the mean phase speed of the waves can be calculated and is found equal to 35 m/s.