ORCID Number
0009-0008-2592-7976
Date of Award
Spring 5-4-2026
Access Type
Thesis - Open Access
Degree Name
Doctor of Philosophy in Engineering Physics
Department
Physical Sciences
Committee Chair
Matthew Zettergren
Committee Chair Email
zettergm@erau.edu
Committee Advisor
Edwin Mierkiewicz
Committee Advisor Email
mierkiee@erau.edu
First Committee Member
Kshitija Deshpande
First Committee Member Email
deshpank@erau.edu
Second Committee Member
Shantanab Debchoudhury
Second Committee Member Email
debchous@erau.edu
Third Committee Member
Leslie Lamarche
Third Committee Member Email
leslie.lamarche@sri.com
College Dean
Jayathi Raghavan
Abstract
There is a robust history of theoretical work on ionospheric plasma patches and their attendant plasma fluid irregularities, particularly within the polar cap region. Within this region though, plasma theory does not always yield tractable problems with succinct analytic solutions that are conceptually illuminating. Observational research methods and techniques, using a multitude of ground-based and in-situ systems, provide insights into this complex environment not always readily achieved through theory alone. Limitations in observational insights exist; however, due to two inherent shortcomings of such systems; sensor observational persistence (in-situ sounding rocket and satellite plasma sensors) and/or sensor spatial resolution (terrestrial systems such as incoherent scatter radars and all sky imagers). Computer modeling and simulation has emerged as a useful tool in efforts to overcome observational limitations and provide an analyzable substantiation of the theoretical framework of ionospheric plasma fluid irregularities. Despite the computational cost with respect to the number of processing units and the total processing time for a particular modeled plasma patch size with a given spatial resolution, modeling efforts can meld aspects of plasma theory and observation into a unified analytic product; one that overcomes the limitations of the other two analysis methods. As an example, numerical simulation affords the opportunity to conduct extensive parametric analysis of foundational ionospheric plasma theory by isolating specific plasma parameters on a select basis while producing long duration simulations at spatial scales not realizable through observation.
The validity of simulation results -- their ability to accurately mimic polar cap ionospheric dynamics -- relies, in some part, on the degree to which the model initial conditions properly replicate polar cap ionosphere configurations at the stage of instability development of interest and the extent to which the model properly captures the relevant theoretical foundation of the plasma dynamics. Within this context then, this research seeks new insights into polar cap plasma patch dynamics through improvements in modeling and simulation techniques. Specifically, the effort will:
- Improve accuracy in model initial conditions through the incorporation, in a select number of simulations, of a more comprehensive observationally-derived plasma parameter data set,
- Employ expanded simulation grid volumes that remove the artificiality of direct plasma patch -- simulation grid boundary interactions that are often the result of the need to use smaller grid volumes due to computing resource limitations,
- Model a range of notional polar cap patches for parametric analysis of patch dynamics at relatively high spatial resolutions (one kilometer) and for an extended period of patch evolution and structuring (one hour); and,
- Employ a numerical model that, in contrast to more simple fluid equation-based models, provides a more comprehensive accounting of issues such as plasma chemistry and energy considerations and their effects on the plasma background state and evolving plasma irregularities.
The focus of the analytic effort is irregularity development within the F-region of the high-latitude ionosphere and for those plasma irregularities driven by interchange instabilities (more specifically, the gradient drift instability) within polar cap patches. Analysis of plasma patch dynamics is done using post-processing software tools with a primary focus on calculations of two-dimensional electron density gradient structuring, distributions of electron density gradient scale lengths, maximum linear plasma instability growth rates, polarization electric fields, plasma flow fields, and spectral analysis of plasma irregularity dynamics.
Results emphasize several significant aspects of the growth of mesoscale (defined as spatial dimensions in the tens to low hundreds of kilometers) plasma patch structures over the one-hour duration of the simulations, including:
- The relative importance of the background electric field in producing bulk charge separation and a corresponding polarization electric field component that determines large-scale structuring characteristics,
- The role of the infinite patch extent in modulating polarization electric field responses, background evolution, and impacts on structure growth,
- The delineation of an electron density gradient scale length threshold for the onset of discernible instability striation formation,
- The tendency for flow- and energy-dependent F-region chemistry to impact growth via increased chemical recombination; and,
- Linear approximation assumptions and simplified linear theory instability growth rate determination are complicated by the magnitudes of generated electric fields and their non-static nature.
Scholarly Commons Citation
Redden, Mark, "Modeling of Polar Cap Ionospheric Patches and Attendant Plasma Instabilities: Initialization from Data and Parametric Analysis" (2026). Doctoral Dissertations and Master's Theses. 959.
https://commons.erau.edu/edt/959
