Date of Award


Document Type


Degree Name

Master of Science


Department of Engineering Physics

First Advisor

Robert D. Loper, PhD.


When considering the neutral constituents in the upper thermosphere and exosphere, helium needs to be accounted for as a major species. As detailed by Emmert [2015], most first-principle models do not consider helium a major species when solving for diffusion and collisions within the atmosphere. First-principle, physics-based models hold a distinct advantage of seasonal variations and spatial resolution over empirical models which leads to a more realistic depiction of the atmosphere. The National Center for Atmospheric Research’s (NCAR) self-consistent, physics-based Thermosphere-Ionosphere-Electrodynamic General Circulation Model (TIE-GCM) has been updated to take into account this neutral constituent in its calculations. The major goal was to characterize this change to the TIE-GCM as a function of altitude as helium becomes a dominant species. A distinct improvement was found in the updated model during lower solar activity conditions and altitudes above 750 km altitudes.

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