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Science 2 June 2006:
Vol. 312. no. 5778, pp. 1366 - 1368
DOI: 10.1126/science.1126389
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Reports

Solar Rotation Effects on the Thermospheres of Mars and Earth

Jeffrey M. Forbes,1* Sean Bruinsma,2 Frank G. Lemoine3

The responses of Earth's and Mars' thermospheres to the quasi-periodic (27-day) variation of solar flux due to solar rotation were measured contemporaneously, revealing that this response is twice as large for Earth as for Mars. Per typical 20-unit change in 10.7-centimeter radio flux (used as a proxy for extreme ultraviolet flux) reaching each planet, we found temperature changes of 42.0 ± 8.0 kelvin and 19.2 ± 3.6 kelvin for Earth and Mars, respectively. Existing data for Venus indicate values of 3.6 ± 0.6 kelvin. Our observational result constrains comparative planetary thermosphere simulations and may help resolve existing uncertainties in thermal balance processes, particularly CO2 cooling.

1 Department of Aerospace Engineering Sciences, University of Colorado, Boulder, CO 80309, USA.
2 Department of Terrestrial and Planetary Geodesy, CNES, 31401 Toulouse, France.
3 NASA Goddard Space Flight Center, Greenbelt, MD 20771, USA.

* To whom correspondence should be addressed. E-mail: forbes{at}colorado.edu

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Science. ISSN 0036-8075 (print), 1095-9203 (online)