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Solar flux variability of Mars' exosphere densities and temperatures
Author(s) -
Forbes Jeffrey M.,
Lemoine Frank G.,
Bruinsma Sean L.,
Smith Michael D.,
Zhang Xiaoli
Publication year - 2008
Publication title -
geophysical research letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.007
H-Index - 273
eISSN - 1944-8007
pISSN - 0094-8276
DOI - 10.1029/2007gl031904
Subject(s) - exosphere , mars exploration program , astrobiology , thermosphere , atmospheric sciences , atmosphere of mars , venus , northern hemisphere , southern hemisphere , environmental science , solar maximum , daytime , latitude , martian , noon , flux (metallurgy) , solar minimum , physics , geophysics , solar cycle , solar wind , ionosphere , astronomy , materials science , ion , quantum mechanics , magnetic field , metallurgy
Using densities derived from precise orbit determination of the Mars Global Surveyor (MGS) spacecraft from 1999 to mid‐2005, the response of Mars' exosphere to long‐term solar change is established and compared to that of Earth and Venus. At Mars, exosphere temperatures (weighted towards high‐latitude Southern Hemisphere daytime conditions) change only 36–50% as much as those at Earth as solar activity increases from solar minimum to solar maximum, whereas the response at Venus is one‐fifth that at Mars. General circulation models suggest that this difference may be strongly influenced by adiabatic cooling associated with the thermosphere general circulation. However, other processes such as differences in CO 2 cooling rates may also be playing a role.