Physics
Scientific paper
Dec 2006
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2006agufmsa52a..02b&link_type=abstract
American Geophysical Union, Fall Meeting 2006, abstract #SA52A-02
Physics
0358 Thermosphere: Energy Deposition (3369), 1650 Solar Variability (7537), 2162 Solar Cycle Variations (7536), 7538 Solar Irradiance, 7969 Satellite Drag (1241)
Scientific paper
We report on major improvements to operational solar energy inputs for use in Jacchia-type empirical thermospheric density models to significantly improve Low Earth Orbit (LEO) satellite drag estimation. Three solar indices, compared to only one in the original Jacchia-type and MSIS-type models, best represent the complex interaction between a) the solar emission source (photosphere, chromosphere, corona), b) the irradiances' penetration into the thermosphere (unit optical depth in the middle and lower thermosphere), and c) the length of time for energy transfer between thermospheric layers, i.e., the thermal process of molecular conduction or the kinetic process of molecular diffusion. We have found that the existing 10.7-cm radio flux (F10.7) solar proxy plus two new solar indices/proxies substantially improve density modeling. First, the new S10.7 index accounts for 75 percent of the daily density variability with a 1-day lag, is reported in units of F10.7, is the chromospheric EUV energy between 26-34 nm as measured by the SOHO SEM instrument, and is absorbed by atomic oxygen above 200 km. Second, the new M10.7 proxy accounts for 12 percent of the daily density variability with a 5-day lag. It is formed by the Mg II core-to-wing ratio reported in units of F10.7, is used as a substitute for the far ultraviolet (FUV) lower chromosphere/photosphere Schumann-Runge Continuum (SRC) energy that is dominated by the 145-165 nm range and has a unit optical depth in the lower thermosphere, and is the main source of thermospheric molecular oxygen dissociation not historically included in Jacchia- and MSIS-type models. Third, the F10.7 proxy accounts for 13 percent of the daily density variability with a 1-day lag, is the transition region/coronal XUV/EUV energy less than 121 nm and has a unit optical depth throughout the thermosphere, being absorbed by many neutral species. We describe the deployment of the new solar indices in an operational system for use by the space systems community that is concerned with LEO satellite drag.
Bouwer S.
Tobiska W.
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