Collisionless shocks are one of the most peculiar phenomena in space where non-linear collective phenomena in the plasma dominate the dynamics. They are believed to be one of the most efficient particle accelerators in the universe, and have internal dynamics that are yet to be fully explored. In this project we aim to understand the interplay between the electrostatic turbulence in the shock ramp and the electron dynamics leading to thermalization across the shock. To do so we first use a machine learning technique to compile a database of shocks crossings observed by magnetospheric multiscale (MMS), which will facilitate both case studies and statistical studies of shocks using MMS. The database contains 2803 shock crossings spanning a period from October 2015 to December 2020. For each crossing we provide key parameters necessary for understanding shock dynamics such as Alfv\'nic Mach number and the angle  between the upstream magnetic field and the vector normal to the shock $\theta_$. We then study whistler waves upstream of 11 quasiperpendicular supercritical shocks. We first apply four spacecraft timing method to magnetic field data from MMS to properly characterize the observed whistler waves. We determine their frequency in the plasma rest frame to range from 0.3 to 1.2 the lower hybrid frequency,their wavelength to range from 0.7 to 1.7 ion inertial length and $\theta_$ to range between $20^\circ$ and $42^\circ$. We then use particle data provided by MMS to show that a reflected beam component in the ion velocity distribution function is in resonance with the observed waves indicating that a kinetic cross field streaming instability (KCFSI) is behind the generation of such waves. Finally a kinetic solver is used to model to observed distribution and reinforce the previous conclusion that the KCFSI is behind the generation of the observed whistlers. We end this thesis by discussing the ongoing projects pertaining to the interaction of electrostatic wave mode determination in the shock ramp and the correlation between whistler waves and electrostatic waves around quasi-perpendicular shocks.

The results of past studies indicate that there is an influence of the presence of a nonzero dusk-dawn i.e. y component of the interplanetary magnetic field(IMF By) on the near-Earth magnetotail. Specifically, on the dusk-dawn component (By) of the magnetic field and plasma ion convection, resulting in interhemispheric asymmetries. This project aimed to investigate whether the same is true for mid-tail distances (around 60 RE downtail, at around the moon distance) by investigating data from the ARTEMIS P1 satellite and the OMNI IMF database. This was done by first filtering the data to only include plasma sheet data using criteria on ion temperature and density, and then constructing averages of both tail By and the ion velocity perpendicular to the magnetic field. These average were constructed separately for clearly positive IMF By (> 3 nT) and clearly negative IMF By (< -3 nT), and separately for the northern and southern plasma sheet. It was found that there is a clear effect of the sign of IMF By on both tail By and ion flows, leading to asymmetries similar to those reported at near-Earth distances. Thus it can be concluded that the presence of clearly nonzero IMF By affects the mid-tail region as well, and potentially the entire magnetotail. While these results are consistent with near-Earth studies, this is the first time the asymmetries due to nonzero IMF By are reported in the mid-tail.

Recently, experimental observations have shown that Polar Mesospheric Summer Echoes PMSE may be modulated by radio wave heating the irregularity source region with a ground-based ionospheric heating facilities. It is clear from these past investigations that the temporal behavior of PMSE during ionospheric heating shows promise as a diagnostic for the associated dust layer. To investigate the temporal behavior of plasma irregularities thought to produce PMSE, this work describes a new model that incorporates both finite diffusion time effects as well as dust charging. The hybrid model utilizes fluid ions described by continuity and momentum equations, electrons whose behavior is determined from quasi-neutrality, and charged dust described by the standard Particle-In-Cell PIC method. The model has been used to investigate the temporal behavior of charged dust associated electron irregularities during electron temperature enhancement associated with radio wave heating. The model predicts that the temporal behavior of the irregularities depends on the ratio of the electron-ion ambipolar diffusion time to the dust particle charging time Td/Tc. The results indicate that typically for Td/Tc << 1, an enhancement in electron irregularity amplitude occurs for a period after turn-off of the radio wave heating. The work also predicts that for Td/Tc >> 1, an enhancement in electron irregularity amplitude occurs for a time period after the turn-on of the radio wave heating. Due to the dependence of Td on irregularity scale-size, these results have important implications for observations of PMSE modification at different radar frequencies. Both continuous and discrete charging model were embedded into this computational model, the results were compared and analyzed. It is evident that significant diagnostic information may be available about the dust layer from the temporal behavior of the electron irregularities during the heating process which modifies the background electron temperature. Particularly interesting and important periods of the temporal behavior are during the turn-on and turn-off of the radio wave heating. Although a number of past theoretical and experimental investigations have considered both these on and off period, this dissertation considers further possibilities for diagnostic information available as well as the underlying physical processes. Approximate analytical models are developed and compared to a more accurate full computational model as a reference. Then from the temporal behavior of the electron irregularities during the turn-on and turn-off of the radio wave heating, the analytical models are used to obtain possible diagnostic information for various charged dust and background plasma quantities. Finally, two experiment campaigns have been performed at HAARP, Gakona, Alaska. Preliminary observation results look promising for the existence of PMSE turn-on overshoot. However, more careful experiments need to be done before firm conclusions can be drawn. The new designed Echotek digital receiver is ready for use now. It will be much superior to the experimental setup used for measurements in the previous campaign.Therefore, future experimental campaigns are planning next year to support the theoretical research. / Ph. D.

Plasma physics emerged in the early 20th century and became a focal point for research after the Second World War due to the potential uses of nuclear fusion.The reasons for this varied from the creation of hydrogen bombs to fusion for energy production. Moreover, with recent developments in semiconductors and nanoscale objects, where quantum effects are non-negligible, a theory of quantum plasma wasrequired. Plasmas can be split into two main regimes, Classical and Quantum, each requiring a separate theory. In this thesis, we introduce the kinetic theory of plasmas. We study the two regimes separately and obtain a description of the plasmas in terms of a phase-space distribution function; a distribution 𝑓 in the classical case, and the quantum analogue in the Wigner function 𝑊. These are governed by the classical Vlasov equation and the quantum analogue in the Wigner equation. The introduction of the Wigner function in Wigner’s article [5] in 1932, made it easier to connect the two theories since theyboth reside within the phase space. To show that the quantum theory is equivalent to the classical theory with the addition of quantum effects, we used perturbation theory, with a perturbation in the form of an electrostatic linear wave. This results in two dispersion relations, one for each regime. These are equal except for a single term, which can be interpreted as quantum effects. This confirms that the two theories are equivalent in the classical limit. Moreover, we introduce the density matrix, a way to describe systems with statistical mixtures of quantum states. This enables us to derive the set of equations known as the BBGKY-hierarchy. In turn, this hierarchy allows us to reduce the number of particles we need to consider, something that comes in handy when dealing with many-particle systems, which otherwise can be close to impossible.

A two-dimensional, time-dependent model and code have been developed to model electrothermal (ET) plasma discharges. ET plasma discharges are capillary discharges that draw tens of kA of electric current. The current heats the plasma, and the plasma radiates energy to the capillary walls. The capillary walls ablate by melting and vaporizing and by sublimation. The newly developed model and code is called the Three-fluid, 2D Electrothermal Plasma Flow Simulator (THOR). THOR simulates the electron, ion, and neutral species as separate fluids coupled through interaction terms. The two-dimensional modeling capabilities made available in this new code represent a tool for the exploration and analysis of the physics involved in ET plasma discharges that has never before been available. Previous simulation models of ET plasma discharges have relied primarily on a 1D description of the plasma. These models have often had to include a tunable correction factor to account for the vapor shield layer - a layer of cold ablated vapor separating the plasma core from the ablating surface and limiting the radiation heat flux to the capillary wall. Some studies have incorporated a 2D description of the plasma boundary layer and shown that the effects of a vapor shield layer can be modeled using this 2D description. However, these 2D modeling abilities have not been extended to the simulation of pulsed ET plasma discharges. The development of a fully-2D and time-dependent simulation model of an entire ET plasma source has enabled the investigation of the 2D development of the vapor shield layer and direct comparison with experiments. In addition, this model has provided novel insight into the inherently 2D nature of the internal flow characteristics involved within the plasma channel in an ET plasma discharge. The model is also able to capture the effects of inter-species interactions. This work focuses on the development of the THOR model. The model has been implemented using C++ and takes advantage of modern supercomputing resources. The THOR model couples the 2D hydrodynamics and the interactions of the plasma species through joule heating, ionization, recombination, and elastic collisions. The analysis of simulation results focuses on emergent internal flow characteristics, direct simulation of the vapor shield layer, and the investigation of source geometry effects on simulated plasma parameters. The effect of elastic collisions between electrons and heavy species are shown to affect internal flow characteristics and cause the development of back-flow inside the ET plasma source. The development of the vapor shield layer has been captured using the diffusion approximation for radiation heat transfer within the ET plasma source with simulated results matching experimental measurements. The relationship between source radius and peak current density inside ET plasma discharges has also been explored, and the transition away from the ablation-controlled operation of ET plasma discharges has been observed. / Ph. D.

Previous plasma imaging missions have used time-delay integration techniques that correct for uniform motion blur during integration. This was due to the assumed constant range-to-target of each pixel in the observed scene. ICON's low orbital altitude and twelve second integration time create non-uniform motion blur across the observed scene and necessitate a novel variable-range time-delay integration (TDI) algorithm be used to spatially resolve the two-dimensional images. The variable-range TDI algorithm corrects for each pixel moving at a different angular rate throughout image integration and transforms each raw image onto a surface where the spacecraft is moving at a constant angular rate with respect to every pixel in the image. Then as the raw images are co-added together the non-uniform motion of the observed scene is accounted for and will not geographically distort the final images, or any features seen within them. Through simulation using output from the SAMI3 model during plasma depletion formation it was determined that the structuring and gradients of plasma depletions can be recovered using this technique. Additionally, the effects of depletion width, solar activity level, and misalignment of the field-of-view with the local magnetic field were investigated. The variable-range TDI technique is able to recover the overall shape and depth of depletion of the depletions in all cases, however the determination of gradients observed at depletion walls is significantly degraded for very narrow plasma depletions and during periods of low solar activity. All simulated model conditions were shown to be representative of current ionospheric conditions. / Master of Science / Equatorial spread-F, also termed plasma bubbles, is a phenomenon that occurs in the equatorial region of Earth’s ionosphere, the charged region of Earth’s atmosphere. Plumes of less dense plasma, the charged material of the Ionosphere, rise through regions of higher density plasma. This causes disturbances to radio signals that travel through this region, which can lead to GPS range errors or loss of signal. ICON is a NASA Explorer mission aimed at, in part, understanding the sources of variability in the ionosphere. One instrument onboard ICON to accomplish this goal is the FarUltraviolet Imager which images airglow in the far-ultraviolet range. During nighttime, the FUV imager can observe plasma bubbles to study the instability and the mechanisms that produce it. This thesis looks at the ability of the variable-range time-delay integration (TDI) algorithm, used to produce images from ICON’s Farultraviolet imager, to spatially resolve the structure and gradients of observed plasma bubbles. However, due to the viewing geometry of ICON’s FUV imager, each pixel across the observed scene experiences a different angular rate of motion blur. The variable-range TDI algorithm removes this non-uniform motion blur by transforming each raw image onto a surface where the spacecraft moves at a constant angular rate with respect to every pixel in the image. Then raw images are integrated together such that the observed scene is not geographically distorted. It was concluded that the TDI process is able to spatially resolve a wide variety of plasma bubbles under various ionospheric conditions and imager configurations.

The Earth’s magnetosheath is a space plasma region consisting of solar wind plasma which is heated and compressed due to interaction with the Earth’s magnetic field. This turbulent region contains coherent structures and various plasma waves which affect the particle dynamics and collisionless energy transfer. In this licentiate thesis, we investigate such processes and where they occur. Through in-situ measurements from NASA’s Magnetospheric Multiscale (MMS) mission, we study whistler waves – electromagnetic, right-hand polarized waves known to heat electrons – and how they interact with electrons. We show how whistler waves are generated by electrons in the turbulent magnetosheath. We also investigate which plasma conditions are favorable for whistler waves to form.

We study plasma density variations within the ionosphere and their effects on trans-ionospheric signals, with a geodetic focus on Sweden from 2014 to 2023. We look for temporal, spatial, seasonal, and solar cycle patterns. We also discuss the percentage of occurrence of ionospheric irregularities and GNSS signal disturbances within the data at hand. We use in situ data collected by ESA-Swarm satellites and ground data provided by the Lantmäteriet-Swepos network ionosphere monitor. We find that high-latitude regions are susceptible to displaying more irregular electron density fluctuations (i.g., polar cap patches) than mid-latitudes. We also find that GNSS signal interference resulting in increased receivers’ positioning uncertainty is predominant at high latitudes. On the other hand, increased positioning uncertainty may be detected at noon in mid-latitude regions, mainly due to solar radiation exposure. Furthermore, hourly geomagnetic effects at high latitudes induce enhanced electron density fluctuations and positioning uncertainty at night. Findings also show more electron density fluctuations around winter and less in summer. Moreover, we find that the solar cycle influences the intensity of electron density fluctuations and positioning uncertainty, with the seasonal effects being more pronounced during periods of increased solar activity. Finally, results show that when ionospheric irregularities are observed, disturbances in GNSS signals may be detected, leading to imprecision in positioning services. Furthermore, we see that the absence of ionospheric irregularities results in a generally safe path for GNSS signals, which is beneficial for positioning accuracy. This comprehensive research enhances our understanding of ionospheric behavior in higher latitude environments and its impact on GNSS signals. Future research in this field could go deeper into the specific mechanisms driving electron density fluctuations and scintillation effects, explore additional geographic regions, and consider longer periods to refine our understanding of ionospheric dynamics and its implications for advanced space weather forecasting and satellite system resilience.

No description available.

An ion trap has been constructed that creates a potential well suitable for confining ions with the space charge of an electron cloud. The trap uses the concept of artificially structured boundaries, regions of overlapping electric and magnetic fields, to confine particles in a relatively field free volume. Measurements are presented from the build-up of ionized molecular hydrogen over time. Molecular hydrogen is introduced into the confinement volume by direct electron bombardment ionization of neutral background H2 leaked into the trap. Detailed analysis of the data is conducted using particle-in-cell simulations of trap operation and rate mechanics analysis. Pressure dependent estimates of ion lifetimes in the trap are on the order of milliseconds. Along with discussion of the trap a full introduction to the particle-in-cell technique is conducted through an original code implementation.