Continuum damping of topologically-protected edge modes at the boundary of magnetized plasma

The topological properties of the magnetized cold gaseous plasma have recently been explored and the existence of topologically protected edge states have been established [1,2]. These studies are limited to undamped edge states [1,2]. Taking a step further, we include collisionless damping of topological edge states at the interface of an inhomogeneous magnetized plasma and vacuum. We find that at the plasma-vacuum interface a continuous spectrum of modes exists. In this continuum, the frequency of the edge state matches with a local upper-hybrid electrostatic mode, and a resonant coupling between the modes results in collisionless damping of the former. Nevertheless, we show using 3D particle-in-cell simulations that edge states remain unidirectional and topologically protected with respect to backscattering. A theoretical model predicting the spatial damping rate will also be presented. These findings broaden the possible applications of these exotic excitations in space and laboratory plasmas.

[1] J. Parker et al, Phys. Rev. Lett. 124, 195001 (2020).

[2] Yichen Fu and Hong Qin, Nature Communications 12, 3924 (2021).