Mathematics – Logic
Scientific paper
Dec 2006
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2006agufmsa11a..02e&link_type=abstract
American Geophysical Union, Fall Meeting 2006, abstract #SA11A-02
Mathematics
Logic
0350 Pressure, Density, And Temperature, 0355 Thermosphere: Composition And Chemistry, 0358 Thermosphere: Energy Deposition (3369)
Scientific paper
Recent analyses of thermospheric total mass densities, derived from changes in the orbits of near-Earth space objects, indicate that there is a climatological F10.7-dependent bias relative to empirical density models such as NRLMSISE-00 and Jacchia-70. This bias is predominantly characterized by a sharp drop-off of the data-to- model density ratios at very low solar activity levels, but deviations are also observed under solar maximum conditions. We consider three potential explanations for this bias: 1) The F10.7 proxy does not provide a sufficiently linear representation of solar extreme ultraviolet (EUV) irradiance, 2) The empirical models are not flexible enough to represent possible non-linearities in the EUV response of thermospheric density, or 3) The climatological response of the thermosphere to EUV irradiance is evolving, possibly as a result of enhanced greenhouse cooling. Using a 40-year database of orbit-derived thermospheric densities, we investigate these possibilities and whether the use of other EUV proxies, such as E10.7 and Mg II, in empirical models improves the models' representation of solar cycle effects. We find that an EUV-dependent bias is observed regardless of which proxy is used, and that evolution of the thermospheric EUV response may be partly responsible for the observed F10.7-dependent bias in MSIS (the model is largely based on pre-1985 data). When the bias curves from successive solar cycles are compared, the use of F10.7 produces the most self-consistent results.
Emmert John T.
Lean Judith L.
Marcos Frank A.
Picone Michael J.
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