Flux-driven algebraic damping of m=2 diocotron mode

Recent experiments with pure electron plasmas in a Malmberg-Penning trap have observed the algebraic damping of $m=2$ diocotron modes.\footnote{A.A. Kabantsev \textit{et. al.}, Phys. Rev. Lett. \textbf{112}, 115003, 2014.} Due to small field asymmetries a low density halo of electrons is transported radially outward from the plasma core, and the mode damping begins when the halo reaches the resonant radius $r_{\text{res}}$, where $f=mf_{E\times B}(r_{\text{res}})$. The damping rate is proportional to the flux of halo particles through the resonant layer. The damping is related to, but distinct from the exponential spatial Landau damping in a linear wave-particle resonance. This poster uses analytic theory and simulations to explain the new flux-driven algebraic damping of the mode. As electrons are swept around the nonlinear ``cat's eye" orbits of the resonant wave-particle interaction, they form a quadrupole $(m=2)$ density distribution, which sets up an electric field that acts back on the plasma core. The field causes an $E\times B$ drift motion that symmetrizes the core, i.e. damps the $m=2$ mode.