Inviscid damping of a perturbed elliptical vortex in an ExB strain flow in nonneutral electron plasmas

The inviscid spatial Landau damping of the oscillation of a perturbed two-dimensional (2D) vortex under an applied external strain flow is studied using an electron plasma confined in a Penning-Malmberg trap. The experiments exploit the unique properties of magnetized, single-component plasmas to study 2D vortex dynamics through the isomorphism between the 2D Drift-Poisson equations that describe plasma E x B drift dynamics and the Euler equations that describe inviscid incompressible fluid flows. An imposed external strain field is produced by fixing the electrical potential at the boundary. An elliptical vortex patch under a constant strain flow undergoes nutation. With a finite peripheral vorticity gradient, the oscillatory motion of the vortex damps towards a stationary elliptical equilibrium state. The damping rate is found to be independent of strain rate for quasi-flat vortices and is determined by the initial state of the system. Vortex-in-cell simulation results for non-linear effects such as separatrix crossing of peripheral vorticity and interactions with the harmonics of the fundamental resonance will also be discussed.