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An experiment to measure variations in nighttime E ‐region neutral concentration
Author(s) -
Cogger L. L.,
Carlson H. C.
Publication year - 1977
Publication title -
radio science
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.371
H-Index - 84
eISSN - 1944-799X
pISSN - 0048-6604
DOI - 10.1029/rs012i002p00261
Subject(s) - thermosphere , airglow , incoherent scatter , daytime , ionosphere , atmosphere (unit) , atmospheric sciences , environmental science , physics , line (geometry) , computational physics , meteorology , mathematics , geophysics , geometry
The entire thermosphere responds strongly to changes in the composition and relative number density of the upper atmosphere near 100 km. However, the atmosphere at altitudes near 100 km is difficult to probe experimentally, and complex to treat theoretically. Time‐continuous incoherent scatter daytime observations of profiles of ion‐neutral collision frequencies υ in (providing net neutral concentration) and neutral temperatures T n have significantly extended our knowledge of this region over the past few years, but low signal strengths have to date precluded application of that technique to the nighttime period. Here, an experimental procedure is demonstrated which holds serious potential for the nighttime measurement of υ in by combining incoherent scatter data with appropriate photometric measurements. Data illustrating the technique are applied to comparing, near 100 km, relative variations in atomic oxygen concentrations n (O) (from the E ‐region component of the OI 5577 Å emission) to those in υ in or net neutral concentration (from combined incoherent scatter data and T n extracted from Fabry‐Perot measurement of the OI 5577 Å spectral line profile). For the data presented, the independently determined variations in these two concentrations vary in close proportion to one another, supporting the validity of studying the dynamical behavior of the atmosphere near 100 km by analyzing the temporal variation of the 5577 Å E ‐region airglow.