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.

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.

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.

High-Power Microwaves (HPM) can be used to intentionally disturb or destroy electronic equipment at a distance by inducing high voltages and currents. This thesis presents results from experiments with a narrow band HPM source, the vircator. The high voltages needed to generate HPM puts the vircator under great stress, especially the electrode materials. Several electrode materials have been tested for endurance and their influence on the characteristics of the microwave pulse. With the proper materials the shot-to-shot variations are small and the geometry can be optimized in terms of e.g. output power or frequency content. Experiments with a resonant cavity added to the vircator geometry showed that with proper tuning of the cavity, the frequency content of the microwave radiation is very narrow banded and the highest radiated fields are registred. Since HPM pulses are very short and have high field strengths, special field probes are needed. An HPM pulse may shift in frequency during the pulse so it is very important to be able to compensate for the frequency dependence of the entire measurement system. The development and use of a far-field measurement system is described. / QC 20110616

Following previous studies, a theoretical model for the induced magnetic field by Europa, one of Jupiter's icy moons, is presented. The aim of the model is to find evidence for the existence of a sub-surface ocean on the moon. Moreover, the accuracy of the theoretical model is evaluated using data from the Galileo space probe and a discussion of improvements, with the upcoming mission JUICE in mind, is given. The magnetic field from Jupiter is modeled using a dipole field and the moon is assumed to have the properties of a perfect homogeneous conductive layer (i.e a superconductor with no resistance). Europa is assumed to possess an electrically conductive subsurface ocean with conductivity $\sigma$. As the moon orbits Jupiter, the moon will experience a time-varying magnetic field since the magnetic dipole axis is tilted with an angle with respect to the rotation axis of the planet. The fact that the moon experiences a time-varying magnetic field will cause an inductive response inside the moon if a conductive material is present.  However, since this set-up reflects the ideal case, a discussion of constraints and improvements is submitted as a compliment. This thesis shows that the ocean model for Europa is supported, but further evidence is needed to fully understand the structure of the moon. The model shows a clear induction in almost all Galileo-flybys investigated, especially flyby E4 and E14. Thereby, it can be argued that the model gives a representative picture of the true induced magnetic field, with room for improvement.  In conclusion, further data is needed to fully reveal the structure of the moon, a fact that lays the foundation for the coming JUICE mission. JUICE will study both the magnetic and the electric field of Jupiter, and analyze the inner structures of the Galilean moons with higher precision than ever

This work studies the current collected by the spherical Langmuir probes to be mounted on the ESA Swarm satellites in order to quantify deviations from idealized cases caused by non-ideal probe geometry. The finite-element particle-in-cell code SPIS is used to model the current collection of a realistic probe, including the support structures, for two ionospheric plasma conditions with and without drift velocity. SPIS simulations are verified by comparing simulations of an ideal sphere at rest to previous numerical results by Laframboise parametrized to sufficient accuracy. It is found that for probe potentials much above the equivalent electron temperature, the deviations from ideal geometry decrease the current by up to 25 % compared to the ideal sphere case and thus must be corrected if data from this part of the probe curve has to be used for plasma density derivations. In comparison to the non-drifting case, including a plasma ram flow increases the current for probe potentials around and below the equivalent ion energy, as the contribution of the ions to the shielding is reduced by their high flow energy.

In this work we have studied linear wave propagation in magnetized plasmas using a fully relativistic kinetic equation of spin-1/2 particles in the long scale approximation. The linearized kinetic equation is very long and complicated, hence we worked with restricted geometries in order to simplify the calculations. The dispersion relation of the relativistic model was calculated and compared with a dispersion relation from a previous work at the semi-relativistic limit. Moreover, a new mode was discovered that survives in the zero temperature limit. The origin of the mode in the kinetic equation was discussed and derived from a non-relativistic kinetic equation from a previous work.

We have used Cassini measurements of electron density from Saturn's magnetosphere to search for a plasma tail behind the moon Titan. Such a plasma tail would consist of plasma that manage to escape Titan's gravitational pull and leave Titan's ionosphere to contribute to the plasma distribution in the Saturn system. The Cassini spacecraft was in orbit around Saturn for 13 years and performed 127 close flybys of Titan as well as many passes through Titan's orbit within the planets plasma-filled magnetosphere. We have used measurements of electron density from the Langmuir probe instrument, built by the Swedish Institute of Space Physics in Uppsala to search for such a tail. The data was analyzed in terms of looking at the spatial distribution of plasma around Titan and Saturn by examining the plasma density in Titan’s orbit in comparison to the rest of system, as well as comparisons of plasma density in front of Titan and behind Titan. The analysis provided no evidence of an extended plasma tail or torus.