Open AccessModeled and observed N 2 Lyman‐Birge‐Hopfield band emissions: A comparison
Author(s) -
Eastes R. W.,
Murray D. J.,
Aksnes A.,
Budzien S. A.,
Daniell R. E.,
Krywonos A.
Publication year - 2011
Publication title -
journal of geophysical research: space physics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.67
H-Index - 298
eISSN - 2156-2202
pISSN - 0148-0227
DOI - 10.1029/2010ja016417
Subject(s) - satellite , altitude (triangle) , physics , airglow , computational physics , thermosphere , ionosphere , remote sensing , atmospheric sciences , atmospheric models , spectrograph , environmental science , meteorology , spectral line , geophysics , astronomy , geology , geometry , mathematics
A thorough understanding of how the N 2 Lyman‐Birge‐Hopfield (LBH) band emissions vary with altitude is essential to the use of this emission by space‐based remote sensors. In this paper, model‐to‐model comparisons are first performed to elucidate the influence of the solar irradiance spectrum, intrasystem cascade excitation, and O 2 photoabsorption on the limb profile. Next, the observed LBH emissions measured by the High resolution Ionospheric and Thermospheric Spectrograph aboard the Advanced Research and Global Observation Satellite are compared with modeled LBH limb profiles to determine which combination of parameters provides the best agreement. The analysis concentrates on the altitude dependence of the LBH (1,1) band, the brightest LBH emission in the observations. In the analysis, satellite drag data are used to constrain the neutral densities used for the data‐to‐model comparisons. For the average limb profiles on two of the three days analyzed (28, 29, and 30 July 2001), calculations using direct excitation alone give slightly better agreement with the observations than did calculations with cascading between the singlet electronic N 2 states (a 1 Π g , a′Σ − u , and w 1 Δ u ); however, the differences between the observed profiles and either model are possibly greater than the differences between the models. Nevertheless, both models give excellent agreement with the observations, indicating that current models provide an adequate description of the altitude variation of the N 2 LBH (1,1) band emissions. Consequently, when using the LBH bands to remotely sense thermospheric temperatures, which can be used to provide an unprecedented view of the thermosphere, the temperatures derived have a negligible dependence on the model used.