Trapped-Particle Asymmetry Modes in Single-Species Plasmas

Novel trapped-particle asymmetry modes propagate on cylindrical electron columns when axial variations in the wall voltage cause particle trapping. These modes consist of $\mathbf{E}\times \mathbf{B}$ drifts of edge-trapped particles, partially shielded by axial flows of interior untrapped particles. A simple model agrees well with the observed frequencies and eigenfunctions, but the strong mode damping is as yet unexplained. These modes may be important in coupling trap asymmetries to particle motions and low frequency $\mathbf{E}\times \mathbf{B}$ drift modes.