Simulation of the Kelvin-Helmholtz instability and the excitation of waveguide modes

The Kelvin-Helmholtz instability, an instability driven by shear flows in a plasma or fluid, is a mechanism for transport and current generation at the magnetopause. It has also been used to explain auroral curls. Shear flows have also been suggested as a mechanism to form waveguide modes in the magnetosphere that would then couple with shear Alfvén waves to form field line resonances. Using a magnetohydrodynamic simulation, this thesis will describe simulations of the Kelvin-Helmholtz instability under conditions appropriate to the magnetopause to determine if the Kelvin-Helmholtz instability occurs and whether the instability transports momentum and generates field-aligned current that could produce auroral curls. This thesis presents results of a more comprehensive study of the effect of magnetic field angle on momentum transport and the Kelvin-Helmholtz instability. The three-dimensional simulation of the Kelvin-Helmholtz instability will study the effect of ionospheric conductivity on the instability. In particular, this thesis will study how hemispheric differences in ionospheric conductivity change the evolution of the Kelvin-Helmholtz instability. This thesis presents results from the first nonlinear simulation of the excitation of waveguide modes by a velocity shear and will discuss the conditions under which waveguide modes are excited by shear flows and how nonlinear effects modify the stability of waveguide modes. The results of this study show that the Kelvin-Helmholtz instability is stabilized by a large magnetic shear and also by high conductivity. Another result is that the waveguide mode can be disrupted by vortex formation.