Speaker: Noah Hurst, WiPPL, UW-Madison Physics Department
Abstract: The self-organization of fluids and plasmas into coherent structures has important consequences for their dynamics and transport, particularly with regard to fusion plasmas and geophysical fluids. Dedicated efforts to understand the life-cycle of these structures are needed, including their formation, dynamics, and stability. Discussed here are a series of experiments with non-neutral pure electron plasmas that follow an interesting trajectory from antimatter technology to studies of coherent vortices in two-dimensional (2D) fluids. The apparatus used for electron plasma vortex dynamics relies on an isomorphism between the plasma ExB drift motion and the 2D ideal fluid equations. The vortices are subjected to external flows to investigate their dynamics and stability, thus recreating in a controlled environment the conditions they might experience in the wild. Experiments are presented regarding vortex oscillations due to applied strain flows, adiabatic vortex behavior in time-dependent strain, spatial Landau damping of vortex modes, the Kelvin-Helmholtz instability within a background strain flow, and the splitting of initially elliptical vortices into multiple pieces. The experimental results are compared to particle-in-cell simulations and simple theoretical models when possible. Finally, opportunities for future work are described involving vortex dynamics, other types of coherent structures in plasmas and fluids, and non-neutral plasma physics.