Lower thermospheric infra-red emissions from minor species during high-latitude twilight—A. Experimental results

Abstract

During the DYANA campaign, thermospheric infra-red emissions of CO 2( v 2), CO 2( v 3), O 3( v 3) and NO ( ΔV = 1) were measured by a rocket-borne liquid helium-cooled spectrometer on 6 March 1990 above Kiruna, Sweden. The measured radiances are compared with the results obtained during other flights of the same instrument. According to the measured data the 15 μm band of CO 2 is in local thermodynamic equilibrium up to about (100 ± 5) km. Recently proposed high rate constants for the excitation of CO 2( v 2) in atomic oxygen collisions are verified by the measured data. The nitric oxide cooling rate in the lower thermosphere is found to be remarkably constant during different rocket soundings. A comparison between the measurements and a non-LTE model is given in part B of this paper; ( Ratkowski et al., 1994, J. atmos. terr. Phys. 56, 1899–1914).