Ground‐based observation of high‐altitude, high‐temperature emission in the O 2 atmospheric band nightglow
2003; American Geophysical Union; Volume: 108; Issue: A7 Linguagem: Inglês
10.1029/2003ja009885
ISSN2156-2202
AutoresT. G. Slanger, P. C. Cosby, D. L. Huestis,
Tópico(s)Atmospheric chemistry and aerosols
ResumoO 2 ( b 1 Σ g + − X 3 Σ g − ) atmospheric band emission, when viewed from the ground outside the auroral zone, is considered to originate in the 90–100 km altitude region, from O‐atom recombination. However, the v = 0,1 levels of the b 1 Σ g + state can also be generated through an energy transfer process, when O( 1 D) collides with O 2 . In the absence of specific altitude information, as in ground‐based measurements, the two sources can still be distinguished because of different characteristic temperatures. We have analyzed sky spectra from the Keck I and II telescopes on Mauna Kea, contrasting solar minimum and maximum conditions and variations with time of night. Utilizing the O 2 ( b ‐ X ) 1‐1 band, we find that in averaged solar minimum conditions, ∼75% of the emission comes from an altitude corresponding to 200 K, while ∼25% has a temperature near 700 K and therefore originates at high altitude. The fraction of high‐temperature emission is often considerably greater early in the evening. At solar maximum, the high altitude component can be dramatically enhanced in the early evening; emission in the 1‐1 band reaches intensitities of 100–150 R, with a rotational temperature near 1000 K. We also observe high‐J b ‐ X 0‐0 band lines penetrating the Fraunhofer A‐band region, the normal absorption becoming emission. Emission intensites deduced from such observations indicate that the ionospheric 0‐0 band is at least as intense as the 1‐1 band, as expected.
Referência(s)