UC San Diego

Kinetic models are often necessary to adequately describe plasma dynamics. Firstly, important kinetic effects in plasmas can persist even in a fluid parameter regime, such as the thermal force in the Braginskii model. Secondly, many plasmas of interest – such as occur in laser-plasma interactions – are far from the thermal equilibrium assumed by fluid models, and must be described using the Vlasov equation.Direct kinetic simulations of plasmas are computationally expensive. Therefore, reduced models and simplified problem setups are instrumental to the study of kinetic plasma effects. This dissertation is divided into three projects, each addressing kinetic plasma effects with a reduced model. The first project investigates relativistic electron dynamics in the presence of colliding laser pulses. The stochastic dynamics of an electron in counter-propagating linearly polarized laser beams is analyzed using a recently developed 3/2-dimensional Hamiltonian approach. It is shown that perpendicular canonical momenta suppress stochasticity, helping to explain the results from recently reported numerical studies of stochastic dynamics in a similar setting. The stochasticity in a perpendicular polarization setup is demonstrated. Lastly, the impact of radiation friction effects is considered, and shown to be negligible in the classical radiation reaction limit. The second project investigates electron dynamics during laser-target interaction. The model is proposed to describe the laser-driven electron acceleration that occurs when a high-intensity laser interacts with a nanoplate target. Formation of the quasi-static electric and magnetic fields is described, and the residual between these static fields is shown to be crucial for stochastic the electron acceleration beyond the ponderomotive scaling. The third project is dedicated to reduced modeling of Coulomb collisions in gyrokinetic simulations. A linearized multi-species model collision operator is adapted for the continuum gyrokinetic code COGENT. It is used to simulate highly collisional plasmas to illustrate that the operator recovers both friction and thermal forces of the Braginskii fluid model. The neoclassical transport of heavy impurities simulated with COGENT is shown to agree with previously published theoretical results.