Master of Science, Miami University, 2013, Computational Science and Engineering

The objective of this thesis is to present in-depth analyses and characterization of GNSS ionosphere scintillation signals in the time-frequency domain. The spectral analysis tool used in this work is an adaptive periodogram technique (APT). Recent studies have demonstrated that APT can generate high resolution time-frequency information for both carrier phase and signal intensity of GNSS scintillation signals. Using APT, it was possible to analyze the spectral characteristics of ionosphere scintillations from various latitudes based on receiver measurements from Alaska (62.4°N), Hong Kong (22.3°N) and Singapore (1.4°N). The results show that during persistent phase scintillation events, high frequency components tend to appear more often and last longer at high latitude regions than at low latitude and equatorial regions. Also, by applying APT to the front end data collected by our antenna array in Gakona, Alaska, it was possible to estimate the background ionosphere plasma drift velocity. The result compared favorably against the plasma drift measurements obtained by the SuperDARN radar located at nearby Kodiak, Alaska.

Committee: Yu Morton PhD (Advisor); Qihou Zhou PhD (Committee Member); Chi-Hao Cheng PhD (Committee Member) Subjects: Electrical Engineering

Doctor of Philosophy, Case Western Reserve University, 2023, EECS - Electrical Engineering

The ionosphere occupies a privileged position in the geospace system, perturbed by space weather in the magnetosphere above and by terrestrial weather in the electrically neutral atmosphere below, which enables its use as a tool for detection of geophysical signatures in adjacent systems. Ionospheric measurements have been a subject of interest since the dawn of radio. Today, the increased availability of computing power and data storage stands to enable significant strides in frontier questions in aeronomy. However, the costs of constructing and maintaining measurement networks limits the density and cadence of available measurements. This work describes the design and deployment of a modular, low-cost sensing network which uses the well-established technique of Doppler measurement of the carrier signals from atomic-clock beacon stations, such as the National Institute of Standards and Technology stations WWV and WWVH, as a proxy measurement for change in virtual ionospheric height. Four sections are presented: An introduction to the citizen scientists of the amateur radio community, the results of a pilot experiment conducted on the occasion of WWV's hundredth anniversary, documentation of hardware, and the data collected by the stations deployed at the time of writing. This community-supported network of stations act together as a meta-instrument to address the problem of undersampling in the geospace environment.

Committee: Christian Zorman (Advisor); Steven Hauck III (Committee Member); David Kazdan (Committee Member); Francis Merat (Committee Member) Subjects: Atmospheric Sciences; Electrical Engineering; Remote Sensing

Master of Science (MS), Wright State University, 2020, Physics

A one-dimensional kinetic particle-in-cell (PIC) MATLAB simulation was created to demonstrate the time-evolution of various plasma distributions. Building on previous plasma PIC programs written in FORTRAN and Python, this work recreates the computational and diagnostic tools of these packages in a more user- and educational-friendly development environment. Plasma quantities such as plasma frequency and species charge-mass ratios are arbitrarily defined. A one-dimensional spatial environment is defined by total length and number and size of spatial grid points. In the first time-step, charged particles are given initial positions and velocities on a spatial grid. After initialization, the program solves for the electrostatic Poisson equation at each time step to compute the force acting on each particle. Using the calculated force on each particle and the “leap-frog” method, the particle positions and velocities are updated and the motion is tracked in phase-space. Modifying parameters such as spatial perturbation, number of particles, and charge-mass ratio of each species, the time-evolution for various distributions are examined. The simulated distributions examined are categorized as the following: Cold Electron Stream, Electron Plasma Waves, Two-Stream Electron Instability, Landau Damping, and Beam-Plasma. The time evolution of the plasma distributions was studied by several methods. Tracking the electric field, charge density and particle velocities through each time step yields insight into the oscillations and wave propagation associated with each distribution. One key diagnostic missing from the original FORTRAN code was the electric field dispersion relation. The numerical dispersion relation allows for further insight into modelling plasma oscillations/waves in addition to the kinetic/field energies and electric field tracking present in the original code. Simulated results show agreement with other kinetic simulations as well as plasma theory.

Committee: Amit Sharma Ph.D. (Advisor); Ivan Medvedev Ph.D. (Committee Member); Sarah Tebbens Ph.D. (Committee Member) Subjects: Atmospheric Sciences; Atoms and Subatomic Particles; Physics; Plasma Physics

Master of Science, Miami University, 2017, Computational Science and Engineering

The focus of this thesis is to characterize the variability of the helium ion fraction in the topside ionosphere using incoherent scatter radar (ISR) from Arecibo Observation, Puerto Rico. The thesis centers on two aspects: The first one is to present the phenomenon of helium ion fraction with solar cycle, season, and day-and-night. This study firstly reports the seasonal phenomenon of helium ion fraction from 400 km to 700 km in detail at solar maximum over Arecibo. The second one is to analyze the mechanism of seasonal phenomenon of helium ion fraction. The results show downward ion flow plays an important role in seasonal variation of the helium ion fraction.

Committee: Qihou Zhou (Advisor); Donald Ucci (Committee Member); Dmitriy Garmatyuk (Committee Member) Subjects: Electrical Engineering

Doctor of Philosophy (PhD), Wright State University, 2017, Environmental Sciences PhD

This research dramatically increase radiation efficiency of very low frequency (VLF) and extremely low frequency (ELF) antenna in the ionosphere by implementing a concept of a parametric antenna. The research addresses the interaction of the electromagnetic waves in the atmosphere; analyzes the radiation efficiency of different types of RF frequencies (ex: Very low Frequency (VLF) and Extremely Low Frequency (ELF)); and includes different types of antennas, such as dipole and loop antennas, in the ionosphere environment and simulating the differences to verify the parametric antenna concept. This VLF analysis can be performed many ways and this VLF frequency is widely used in space antennas by both military and civilian elements. The VLF waves in the ionosphere are used to create high levels of density irregularities in the radiation belt region and to deflect the energetic electrons and ions from the region to prevent their negative effects on satellite electronics (including the antenna). Therefore, this research addresses the problem of low radiation efficiency of satellite based antenna on conventional loop and dipole antennas used for excitation of electromagnetic VLF/ELF waves in the ionosphere. The research results will be used in the field of ionospheric plasma physics research with applications in satellite space experiments. In particular, the results will be influential in the area of active space experiments for the removal of highly energetic particles in the ionosphere which are harmful to satellite electronics, VLF/ELF communications, and for different commercial applications. This research first looks at a theoretical solution followed by modeling and simulation to prove the parametric antenna concept. Finally, experimentation was performed in the laboratory to validate and verify a theoretical solution and modeling and simulation of parametric antenna.

Committee: Amit Sharma Ph.D. (Committee Co-Chair); Doug Petkie Ph.D. (Committee Co-Chair); Chris Barton Ph.D. (Committee Member); Ernie Hauser Ph.D. (Committee Member); Vladimir Sotnikov Ph.D. (Committee Member) Subjects: Environmental Science

Doctor of Philosophy, The Ohio State University, 1963, Graduate School

Committee: Not Provided (Other) Subjects: Engineering

Master of Science, Miami University, 2015, Computational Science and Engineering

Incoherent scatter radar (ISR) is a versatile tool to study the ionosphere by measuring the autocorrelation function (ACF). Accurate ACF in the E-region is difficult to obtain because the relative short range limits the length of a pulse. The short correlation time of the ionosphere renders the correlation using the pulse-to-pulse technique useless. In the thesis, we study a method that combines intra-pulse and inter-pulse techniques and apply it to the data taken at Arecibo Observatory. We show simultaneously measured ACF's at short and long lags and summarize the merits of ACF. Applications of ACF and its advantages are discussed. The technique used here will make the derivation of ionosphere parameters more accurate.

Committee: Qihou Zhou (Advisor); Chi-Hao Cheng (Committee Member); Dmitriy Garmatyuk (Committee Member) Subjects: Aeronomy; Aerospace Engineering; Computer Engineering; Computer Science; Earth; Radiology

Master of Science, Miami University, 2014, Computational Science and Engineering

Ionosphere scintillation is a phenomenon by which irregularities in the ionosphere interfere with radio signal propagation. This causes large errors in Global Positioning System (GPS) receivers and sometimes loss of lock of satellite signals. The goal of this research is to develop advanced receiver algorithms for all GPS bands to minimize the impact of ionosphere scintillation. Results have been obtained from equatorial and high latitude scintillation data collected in Ascension Island and Alaska, respectively, and compared to a Septentrio PolaRxS commercial receiver. The results show differences and improvements over the Septentrio PolaRxS. This research will serve to guide in the development of future Global Navigation Satellite System (GNSS) receivers and provide a greater understanding of the effect of scintillation on new GNSS signals.

Committee: Yu Morton PhD (Advisor); Dmitriy Garmatyuk PhD (Committee Member); Eric Vinande PhD (Committee Member) Subjects: Computer Engineering; Electrical Engineering

Doctor of Philosophy, The Ohio State University, 2007, Geodetic Science and Surveying

One of the major error sources in using Global Positioning System (GPS) measurements for modeling the ionosphere is the receiver differential code bias (DCB). Therefore, the determination of the receiver DCB is important, and to date, it has been done mostly using the single-layer ionospheric model assumption. In this dissertation, a new and efficient algorithm using the geometry conditions between the satellite and the tracking receivers is proposed to determine the receiver DCB using permanent reference stations. In this method, an assumption that ionosphere is represented by a single-layer model is not required, which makes DCB computation independent on the pre-selected ionosphere model. In addition, this method is simple, accurate and computationally efficient. The principal idea is that the magnitude of the signal delay caused by the ionosphere is, under normal conditions, highly dependent on the geometric range between the satellite and the receiver. The proposed algorithm was tested with the Ohio Continuously Operating Reference Stations (CORS) and the Transantarctic Mountains Deformation (TAMDEF) sub-network data. The results show that quality comparable to the traditional DCB estimation method is obtainable with greater computational efficiency and simple algorithmic implementation.

Committee: Dorota Grejner-Brzezinska (Advisor) Subjects: Geodesy

Master of Science, Miami University, 2012, Computational Science and Engineering

Ionosphere scintillation impacts GNSS receiver performance. The scintillation effects are measured by two scintillation indices, the amplitude scintillation index S4 and the phase scintillation index sigma_phi. These indices are computed from detrended signal power and carrier phase obtained from the receiver tracking loop outputs, respectively. Recent studies show that the values of these indices depend on the detrending method used to remove the non-scintillation effects. This thesis presents our investigation of the error sources in the scintillation detrending methods. For amplitude scintillation, the main error source is the detrending filter group delay. For phase scintillation, inappropriate detrending filter cutoff frequency selection is the dominant error contributing factor. The paper presents the error assessment and correction techniques for both detrending methods, and the resulting correlations between amplitude and phase scintillations.

Committee: Jade Morton Dr. (Advisor); Chi-Hao Cheng Dr. (Committee Member); Peter Jamieson Dr. (Committee Member); Wouter Pelgrum Dr. (Committee Member) Subjects: Electrical Engineering

Master of Science, Miami University, 2012, Computational Science and Engineering

Because of deficiencies in sampling resolution and storage space, the plasma line frequency component of the incoherent scatter radar (ISR) spectrum has been neglected in experimentally verifying ionospheric parameters. Several incoherent scatter theories were independently developed with confirmation from low resolution data in the 1960s that used the plasma line resonant frequency and plasma line peak intensity to derive ionospheric parameters. Now that higher resolution measurement techniques exist, this thesis investigates three methods for obtaining plasma line resonant frequency, peak intensity, and spectral width. Following this study, several salient features endemic to the ISR experiment performed on January 15-17th, and January 22nd of 2010 are presented and analyzed.

Committee: Qihou Zhou PhD (Advisor); Jade Morton PhD (Committee Member); Chi Hao Cheng PhD (Committee Member) Subjects: Aeronomy; Electrical Engineering; Plasma Physics

Master of Science, Miami University, 2012, Computational Science and Engineering

This thesis reports the investigation of the dynamics and associated phenomena occurring in the ionospheric E- and F-region heights above Arecibo. The observational data was derived with an incoherent scatter radar (ISR) from Arecibo Observatory, Puerto Rico. The thesis focuses primarily on two aspects. One is to study the atmospheric tidal and planetary waves. This is the first time that dual-beam ISR has been used for E- and F-region tidal and planetary wave studies. The vertical structures of the observed tidal and planetary waves are analyzed rigorously. This study is the first to report the existence and possible excitation mechanism of a terdiurnal tide in the F-region at low latitude. The second aspect is to give a more complete explanation of the midnight collapse phenomenon. The F-region electric field, ambipolar diffusion, and tidal components in the meridional wind all play a role in causing the midnight collapse at Arecibo.

Committee: Qihou Zhou PhD (Advisor); Jade Morton PhD (Committee Member); Dmitriy Garmatyuk PhD (Committee Member) Subjects: Aeronomy; Engineering