Abstract
Did you know that in the vacuum of space, there is no vacuum? In fact, most of space is filled with charged particles in a plasma state. Close to Earth, Geomagnetic phenomena, space weather, and radio interference such as GPS scintillation are all explained with plasma dynamics. Space is also the largest laboratory we have for plasma physics. It is, therefore, no surprise that accurate measurements of the surrounding plasma of a spacecraft are a part of the foundation for understanding our own ionosphere. A common approach to probing a plasma is with Langmuir probes, which are conducting objects that collect an electrical current, from which we can infer plasma parameters, usually using orbital-motion-limited (OML) theory. It is known that OML will be erroneous under certain conditions. However, due to the complexity and scales of the problem, several sources of error have not been adequately studied and are therefore not well understood or accounted for. In this dissertation, we use Particle-in-Cell simulations to further our understanding by uncovering limits to the idealized OML theory and building models to correct several such error sources. The thesis focuses on charged-neutral collisional effects, the effects of imperfect geometries, and probes in magnetized plasmas.
List of papers
Paper I. S. M. Brask, S. Marholm, F. Di Mare, S. Adhikari, A. Spicher, T. Takahashi, W. J. Miloch “Electron–neutral collisions effects on Langmuir probe in the lower E-region ionosphere”. In: Physics of Plasmas. Vol. 29, no. 3 (2022), DOI: 10.1063/5.0079761. The paper is included in the thesis. Also available at: https://doi.org/10.1063/5.0079761 |
Paper II. S. M. Brask, S. Marholm, W.J. Miloch, R. Marchand “Effects of Guard and Boom on Needle Langmuir Probes Studied with Particle in Cell Simulations”. Journal of Plasma Physics. 2024, 90 (1):905900114. DOI: 10.1017/S0022377823001411. The paper is included in the thesis. Also available at: https://doi.org/10.1017/S0022377823001411 |
Paper III. S. M. Brask, R. Mishra, G. Holen, Y. Miyake, H. Usui, W.J. Miloch “Spherical Langmuir probes in magnetized plasma. A model based on Particle-in-Cell simulations”. Physics of Plasmas, 31, 023506 (2024). DOI: 10.1063/5.0177775. The paper is included in the thesis. Also available at: https://doi.org/10.1063/5.0177775 |