Improvement of TIE-GCM thermospheric density predictions via incorporation of helium data from NRLMSISE-00

Thermospheric neutral densities derived from the CHAMP (CHAllenging Minisatellite Payload) accelerometer data are used to investigate the accuracy of several empirical and numerical thermospheric neutral density model families from solar maximum (year 2002) through solar minimum (year 2008); the Jacchia model, MSIS (Mass Spectrometer Incoherent Scatter) model, and TIE-GCM (NCAR's Thermosphere Ionosphere Electrodynamics General Circulation Model). All show good agreement to the variations of neutral densities from CHAMP, but still have uncertainties which need to be addressed prior to their operational use, such as in the modeling of satellite orbital position. The physics-based TIE-GCM exhibits relatively large deviations from CHAMP (an RMS percent difference at 400 km of 47% over 6 years) as compared to the empirical models (e.g., 10% for the Jacchia-Bowman's model (JB2008)). The uncertainties gradually increase with the declination of the solar activity. Weighted partial pressures of helium from the Naval Research Laboratory's MSIS Extension 2000 (NRLMSISE-00) were incorporated into TIE-GCM to reflect the helium effect in calculating molecular viscosity, thermal conductivity, and specific heat. As a result, the percent difference standard deviation of the TIE-GCM improved to 21%.