Chemical and dynamical processes in the mesospheric emissive layer. First results of stereoscopic observations

M. Faivre, Clemson University
G. Moreels, Observatoire de Besançon, Besançon, France
Pierre-Dominique Pautet, Utah State University
J. Clairemidi, Observatoire de Besançon, Besançon, France
F. Dumont, Observatoire de Besançon, Besançon, France
O. Lorin, Observatoire de Besançon, Besançon, France
F. Colas, Institut de Mécanique Céleste, Observatoire de Paris, Paris, France


[1] The mesospheric emissive layer is an efficient tracer of the dynamical processes propagating in the atmosphere at that level. CCD images in the near infrared taken from the ground at slant angles often reveal the existence of wavy fields. A series of such images has been transformed, using matrix operations, producing a downward satellite-type view that covers a circular area of radius ∼1000 km at the altitude of the layer. The Fourier characteristics of the wave system are measured using a Morlet-type wavelet generator function with horizontal wavelengths of mostly ∼20–40 km and 100–150 km and temporal periods of ∼15–30 min. An oxygen-hydrogen model is used to evaluate the response of the emissive layer to a progressive density wave. The altitude of the layer is modulated with an amplitude of ∼0.8–1.8 km when a density wave propagates vertically. The layer thickness is slightly modulated and is equal to ∼7 km. Stereoscopic pairs of photographs taken simultaneously on 8–9 September 2000 at the Château-Renard and Pic du Midi observatories are used to obtain surface maps of the emission layer barycenter altitude. A stereocorrelation method suitable for low contrast objects without discrete contours is employed. Preliminary results for areas ∼50 × 50 km2 are presented. The surface maps of the layer barycenter altitude depict the existence of waves. They show the same wavy structure and compare favorably with the maps showing the emission intensity.