Flux-driven algebraic damping of m = 1 diocotron mode

Recent experiments with pure electron plasmas in a Malmberg-Penning trap have observed the algebraic damping of $m=1$ diocotron modes.\footnote{A.A. Kabantsev \textit{et. al.}, Phys. Rev. Lett. \textbf{112}, 115003, 2014.} Transport due to small field asymmetries produce a low density halo of electrons moving radially outward from the plasma core, and the mode damping begins when the halo reaches the resonant radius $r_{\mathrm{res}}$, where $f=mf_{E\times B}(r_{\mathrm{res}})$. The damping rate is proportional to the flux of halo particles through the resonant layer. The damping is related to, but distinct from spatial Landau damping, in which a linear wave-particle resonance produces exponential damping. This poster explains with analytic theory and simulations the new algebraic damping due to both mobility and diffusive fluxes. As electrons are swept around the ``cat's eye'' orbits of resonant wave-particle interaction, they form a dipole $(m=1)$ density distribution, and the electric field from this distribution produces an $E\times B$ drift of the core back to the axis, i.e. damps the $m=1$ mode.