Observations and numerical simulations of electrified, medium-scale traveling ionospheric disturbances (MSTIDs) in the nighttime, mid-latitude ionosphere

This work will present an advancement of the physical understanding of medium-scale traveling ionospheric disturbances (MSTIDs). This will be accomplished primarily through an observational study and with the aid of numerical simulations. MSTIDs are instabilities in the ionosphere characterized by vertical displacements in electron density with wavefronts at an angle to the magnetic meridian. The instabilities typically occur at night near mid-latitudes and are electrified. The polarization electric fields within the structure cause the displacement of electron density to form under an unstable configuration. Previous work on MSTIDs has provided the groundwork for the current study of the physical processes that generate the instabilities. A theoretical description provides a basic understanding of how the instabilities develop in the ionosphere, and includes the important parameters that impact the growth rate of MSTIDs. Using 630.0-nm airglow imaging cameras, a climatological study is conducted to establish long-term trends of the instabilities at two longitudinal sectors not previously studied. The low-latitude extent of MSTIDs is also investigated from the observational study. The numerical simulation work utilizes the SAMI3 (Sami3 is Another Model of the Ionosphere) model, which captures the fundamental physics of the ionosphere. The model simulates a ``wedge'' region of the ionosphere for the self-consistent development of MSTIDs. Once MSTIDs are generated in the model, synthetic observations are calculated and compared to observational data found in the literature. In addition, simulation case studies serve to isolate parameters that influence the growth of MSTIDs in SAMI3, gaining further physical insight into their development. Finally, future research directions are provided that utilize the results from the current work