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Abstract Hypotheses concerning processes related to medium‐scale traveling ionospheric disturbances (MSTIDs) are investigated with the application of models and the analysis of observational data. Wave‐packet parameters for MSTIDs from 2011 through 2022 are obtained from OI 6300 Å observations from the Boston University all‐sky imager (ASI) at the Millstone Hill Observatory during periods for which concurrent Millstone Hill (MH) incoherent scatter radar (ISR) observations are available. A combination of a numerical multi‐layer (NML) model for gravity waves (GW) in the thermosphere with the Field‐Line Interhemispheric Plasma (FLIP) model for ionospheric processes and upper‐atmospheric emissions is applied to generate perturbation electron‐density values, which are compared with ISR‐observed perturbation electron‐density values. A detailed comparison is made between model‐generated and ISR‐observed electron density for two cases, and the comparisons show notably good agreement. Twelve other MSTID cases are also described, giving a total of 14 cases. The results confirm that some nighttime MSTIDs at midlatitudes directly correspond to local GWs. They also suggest that some MSTIDs occurring over MH primarily consist of plasma fluctuations without corresponding local neutral fluctuations and that such MSTIDs are more common during winter months. The phase relationship between electron density and neutral vertical velocity variations is examined for two cases. Additionally, the hypothesis that standard thermospheric dynamic molecular viscosity values should be reduced is evaluated, and it is found that this is not supported by the results.