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Thermospheric composition
Author(s) -
Carignan George R.
Publication year - 1975
Publication title -
reviews of geophysics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 8.087
H-Index - 156
eISSN - 1944-9208
pISSN - 8755-1209
DOI - 10.1029/rg013i003p00885
Subject(s) - thermosphere , atmospheric sciences , atmosphere (unit) , altitude (triangle) , atmospheric composition , latitude , environmental science , composition (language) , atmospheric models , climatology , ionosphere , meteorology , geology , geophysics , physics , mathematics , geodesy , linguistics , philosophy , geometry
The period 1971–1974 has been marked by a substantial advance in man's understanding of composition variability in the thermosphere. The global view of the atmosphere that has been provided by satellite observations in concert with radar backscatter measurements has shown a pattern of composition variability that theorists have been able to explain in large part as resulting from dynamic processes. Important progress has been made in defining composition variability at 120 km, which has greatly improved models which previously had fixed boundary conditions at that altitude. The discovery of the early morning maximum in helium abundance and the better definition of diurnal variation in relative composition have provided a basis for more sophisticated dynamical models. Similarly, models of meridional wind systems have been developed which can account for the better‐defined winter enhancements in helium and atomic oxygen. Finally, composition variability has indicated the presence of a high‐latitude heat source which during periods of magnetic activity profoundly modifies the state of the atmosphere. Some important contributions to our improved understanding of thermospheric composition are reviewed in this paper.