Graduation Semester and Year
Spring 2026
Document Type
Dissertation
Degree Name
Doctor of Philosophy in Physics and Applied Physics
Department
Physics
First Advisor
Yue Deng
Abstract
In this dissertation, research on low- and high-latitude electrodynamics and their impacts on the ionosphere-thermosphere system is studied. First, the climatology of E-region neutral wind shears and their ion-neutral coupling processes is examined. Despite their recognized importance in ionospheric electrodynamics, climatological studies of E-region wind shears have been limited by observational coverage. Using ICON MIGHTI observations with unprecedented spatial and temporal coverage, a comprehensive statistical study is conducted. Large wind shears are found to be a frequent phenomenon in the E-region, exhibiting strong dependences on altitude, latitude, season, and local time, with distribution patterns reflecting different global tidal influences. To examine the ionospheric consequences of these shears, the metal-ion version of SAMI3, which removes the assumption of a uniform ExB drift shared by all ion species, is employed. The model is first validated to reproduce E-region ion convergence consistent with wind shear theory at small magnetic declination angles, establishing the necessary simulation foundation for subsequent work. The second study investigates how E-region neutral wind shears influence equatorial plasma bubble (EPB) development through E-F region coupling, an instability that impacts satellite navigation and radio communications. The results reveal that metal ion convergence layer-enhanced Pedersen conductance is not the only suppression mechanism. The horizontal alignment direction of the shear band, whether the shear is in the zonal or meridional direction, and the altitude within the E-region collectively govern EPB development through electrodynamic processes. The shear effect is further found to be timing-dependent, strongly suppressing EPBs during the early growth phase while having little impact during the decay phase. Thirdly, a set of Diffusion High-latitude Electrodynamic Models (DHEMs), comprising DHEM-EP for electric potential and DHEM-AP for auroral precipitation, is developed based on a denoising diffusion probabilistic model (DDPM) to improve the specification of high-latitude electrodynamic forcing in GCMs. DHEMs reproduce large-scale electrodynamic morphology while better capturing storm and substorm variability than empirical models, and reduce the manual data cleaning effort required by data-assimilation approaches such as AMIE. A multi-model approach is adopted for DHEM-AP, where distinct sub-models with tailored conditioning inputs are trained for different magnetospheric activity regimes. In addition, 24-dimensional MLT-sector electrojet indices are incorporated as conditioning inputs to better resolve the MLT-dependent spatial structure of auroral precipitation that global geomagnetic indices alone cannot capture. These results highlight the advantage of machine learning over empirical models in capturing the complex nonlinear relationships between multiple driving conditions and electrodynamic patterns.
License
This work is licensed under a Creative Commons Attribution-NonCommercial-No Derivative Works 4.0 International License.
Recommended Citation
LI, MINJING, "Ionospheric Electrodynamics at Low and High Latitudes and Its Impacts on the Ionosphere-Thermosphere System: Observations and Modeling" (2026). Physics Dissertations-Archive. 190.
https://mavmatrix.uta.edu/physics_dissertations/190