Dynamic Vortex Drag

This thesis explores the concept of dynamic vortex drag resulting from Kelvin wave excitations on vortex cores in thin films of superfluid ^{4}He. In this system, vortex drag is commonly accepted as a significant mechanism for the dissipation of third sound wave motion; however, current models implementing a static drag force have been unable to quantitatively explain anomalous third sound free decay results found in the literature. In this thesis, many possible manifestations of Kelvin wave agitation are explored and are shown to correct the deficiencies of existing static drag theories. It is therefore concluded that vortex drag in thin films of superfluid ^{4}He is most likely a dynamic, and not a static, process.