Date of Award

Spring 1-1-2019

Document Type


Degree Name

Master of Science (MS)


Aerospace Engineering Sciences

First Advisor

Jeffrey P. Thayer

Second Advisor

Eric Sutton

Third Advisor

John Evans


To better deal with the difficult problem of satellite drag and orbit prediction, this thesis derives and presents an improved way of looking at vertical mass transport and composition in the thermosphere, as well illustrates why helium behaves inversely to the major neutral species in the thermosphere. Scale height analysis shows that helium concentrations at 400km can be related to large scale height perturbations from diffusive equilibrium. A study of molecular, thermal, and eddy diffusion show that the magnitude of the effect of each process varies according to the scale height perturbation from diffusive equilibrium, and that molecular diffusion dominates in the thermosphere, especially at high altitudes. Comparison against the atmospheric model TIEGCM show agreement with the derivation's implications for vertical winds and the inverse behavior of helium, while comparison with the MSIS model shows that an averaged empirical model does not have the fidelity necessary to resolve individual transport processes.