Other
Scientific paper
Dec 2001
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2001agufmsa51a0767s&link_type=abstract
American Geophysical Union, Fall Meeting 2001, abstract #SA51A-0767
Other
0310 Airglow And Aurora, 0350 Pressure, Density, And Temperature, 0355 Thermosphere: Composition And Chemistry
Scientific paper
We suggest that global maps of temperature and oxygen-atom density, in the 120-250 km altitude range, can be inferred from space-based observations of the band profiles of O2 Atmospheric band emissions in the 755-785 nm spectral region. Unpublished data from the GLO [1] and MSX [2] programs show that the O2(b-X) 0-0 and 1-1 bands are observable up to 250 km. The width of the rotational band profiles and the relative intensity of O2(b-X) 1-1 emission increase towards higher altitudes. Local kinetic temperatures can be derived from the rotational band profiles, and oxygen atom densities can be derived from the ratio of the O2(b-X) 0-0 and 1-1 intensities. No observational calibration is required, other than spectral response and tangent altitude. For long-term global measurements of [O] and T, the International Space Station would provide an excellent platform. In the thermosphere, O2(b,v=0) and O2(b,v=1) are produced principally by energy transfer from O(1D) to O2. The O(1D) comes from photodissociation of O2, electron impact on O, and dissociative recombination of O2+, with the latter process dominant in the nightglow. At high altitudes both O2(b,v=0) and O2(b,v=1) radiate efficiently, in spite of the long 12-sec radiative lifetime, and their approximately equal emission intensities reflect the known equal production yields. The GLO data show that the relative intensity of O2(b,v=1) emission begins to drop as the altitude is reduced below 200 km. The known rates of quenching in collisions with O2 and N2 are far too small to be effective at such high altitudes, while O2(b,v=0) is unquenched at all altitudes above 100 km. We conclude that the principal quencher of O2(b,v=1) is the ground state of atomic oxygen, O(3P), and infer a rate coefficient of approximately 1x10-11 cm3 s-1. After this rate coefficient has been measured in the laboratory, we will be able to use the ratio of the O2(b-X) 0-0 and 1-1 band intensities to determine the absolute oxygen atom altitude profile. [1] A.R. Broadfoot, unpublished data; [2] J.-H. Yee, unpublished data We are grateful to Lyle Broadfoot for providing us with samples of GLO data, and to the NSF Aeronomy program for support.
Huestis David L.
Slanger Tom G.
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