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Drag Coefficient Constraints for Space Weather Observations in the Upper Thermosphere
  • Valerie E Bernstein,
  • Marcin Dominik Pilinski
Valerie E Bernstein
University of Colorado Boulder

Corresponding Author:valerie.bernstein@colorado.edu

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Marcin Dominik Pilinski
Laboratory for Atmospheric and Space Physics
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The space weather research community relies heavily on thermospheric density data to understand long-term thermospheric variability, construct assimilative, empirical, and semi-empirical global atmospheric models, and validate model performance. One of the challenges in resolving accurate thermospheric density datasets from satellite orbital drag measurements is modeling appropriate physical aerodynamic drag force coefficients. The drag coefficient may change throughout the thermospheric environment due to model dependencies on composition and altitude. As such, existing drag coefficient model errors may be altitude and solar cycle dependent, with greater errors at higher altitudes around 500 km near the oxygen-to-helium transition region. This can lead to errors in orbit-derived density datasets and models. In this paper, inter-satellite density comparisons at ~500 km are evaluated to constrain drag coefficient modeling assumptions. Density consistency results indicate that drag coefficient models with incomplete energy and momentum accommodation produce the most consistent densities, while the standard diffuse modeling approach may not be appropriate at these altitudes. Models with momentum accommodation between 0.5 - 0.9 and energy accommodation between 0.83 - 0.96 may be the most appropriate at upper thermospheric altitudes. Modeling drag coefficients with diffuse gas-surface interactions could lead to errors in derived density of ~25% and in-track satellite orbit prediction uncertainty during solar maximum conditions on the order of hundreds of meters.
May 2022Published in Space Weather volume 20 issue 5. 10.1029/2021SW002977