Topography of the MLT emissive layer resulting from the chemical-dynamical coupling
Abstract
A program of stereo-imagery of the MLT near infrared emissive layer has recently been initiated using two CCD cameras. Two observation modes can be used. The sites are either located side by side at a distance of about 40-50 km or are situated at a distance of ∼ 540 km in a ``vis-a-vis'' observation mode. For each elementary area section observed simultaneously by both cameras, a normalized correlation coefficient for the intensity is computed and the altitude of the barycenter of the layer is calculated. 3-D topographic maps of the centroid altitude are presented for 50x50 km2 areas. These maps are compared with coded maps of the emission intensity. The couple of maps, for amplitude and intensity, show wave structures having comparable wavelengths and some relative phase-shift. Statistics of the barycenter altitude of the layer, in the 85-90 km range, and vertical amplitudes of the waves, 1 to 3 km, are presented. The near infrared emissive layer is an excellent tracer of the dynamical processes at the MLT level, mainly tides and gravity waves. In this region, the coupling between chemical and dynamical processes is strong. In order to investigate the effect of the propagation of a gravity wave on the altitude and intensity of the emissive layer, a 25-150 km photochemical atmospheric model is used. A density periodic perturbation propagating upward is introduced at the altitude of 60 km. The resulting perturbations in the altitude and intensity of the emissive layer are compared with the observational results. We plan to conduct such stereo-imagery observations from other sites in the world in order to obtain an extended description of gravity wave propagation at the MLT level.
- Publication:
-
35th COSPAR Scientific Assembly
- Pub Date:
- 2004
- Bibcode:
- 2004cosp...35.3449F