Propagation and collisionless damping of topologically-protected surface plasma waves in non-uniformly magnetized plasma columns

Recent theoretical studies revealed the existence of topologically-protected surface plasma waves (TSPWs) in cold magnetized plasmas assumed uniform along the direction of a uniaxial magnetic field. Reflections-free propagation of the TSPWs along arbitrarily-shaped plasma boundaries oriented perpendicularly to the magnetic field was shown to be preserved even when their collisionless damping by localized upper-hybrid resonances was accounted for. Here we extend this theory to the realistic case of three-dimensional magnetic field produced by finite-sized magnetic coils. We demonstrate that when TSPWs are launched in the direction of the decreasing magnetic field, they are collisionlessly absorbed within a highly localized (evanescent) region as they propagate away from the magnetic coil. We show that the resulting wave reflection can be negligible -- in clear contrast with conventional wave reflection from the corresponding evanescence regions.