LOWER-THERMOSPHERIC INFRARED EMISSIONS FROM MINOR SPECIES DURING HIGH-LATITUDE TWILIGHT .B. ANALYSIS OF 15 MU-M EMISSION AND COMPARISON WITH NON-LTE MODELS

During the DYANA campaign, a Skylark VI rocket, known as SISSI-1 and c ontaining an infra-red grating spectrometer and other onboard instrume nts including an atomic-oxygen sensor, was launched at dawn twilight f rom Esrange, Kiruna, Sweden. Molecular vibrational emission features o f carbon dioxide at 4.3 and 15.0 mum, nitric oxide at 5.3 mum, and ozo ne at 9.6 mum were measured in the lower thermosphere. The experimenta l results were discussed in part A (Grossmann et al., 1994, J. atmos. terr. Phys. 56, 1885-1897). In this paper (part B), we analyzed the CO 2 15 mum data in terms of the radiative and collisional excitation and loss processes involved and compared the experimental results to non- LTE radiance models. Good agreement is obtained over a range of altitu des and wavelengths between the predictions of the ARC line-by-line no n-LTE radiance code and the experimental data for SISSI-1, as well as between model simulations and data from a similar payload known as M-I 1 launched under drastically different conditions as part of the MAP/W INE campaign. The data sets provide useful opportunities for more stri ngent tests of the important role of atomic oxygen in CO2 15 mum non-L TE radiance models than available until now and for determining the re gion of applicability of the LTE assumption, as well as for investigat ing a lower-thermospheric energy balance.