Upper- and Lower-Hybrid Continuum Damping of Topologically Protected Edge Modes of Magnetized Plasmas

The recent extension of topological ideas to continuous systems with broken time-reversal symmetry, such as magnetized plasmas, provides new insights into the nature of topologically protected surface plasma waves (TSPWs) [1,2]. I will start by demonstrating a unique characteristic of TSPWs propagating above the electron cyclotron frequency: their collisionless damping via coupling to the continuum of localized upper-hybrid resonances inside a smooth plasma-vacuum interface. We show [3] that damped TSPWs retain their unidirectional nature and immunity against backscattering, and that these properties can be used to generate highly localized energy sinks using sheared magnetic field. Next, I will extend the concept of TSPWs to the low-frequency (ion-dominated) [4] topological surface plasma waves (TSPW’s) and demonstrate how such surface waves can be utilized to impart angular momentum to a plasma column via collisionless damping into a continuum of localized lower-hybrid resonances. Finally, I will show how to extend the earlier theories constrained by the assumption of a unidirectional magnetic field and account for realistic magnetic field profiles produced by finite-sized magnetic coils[5]. The results of our 3D particle-in-cell simulations applied to the parameters of the Penning discharge plasma experiment [6] at PPPL will be presented.

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

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

[3] Roopendra S Rajawat, V. Khudik and G. Shvets, Phys. Rev. Lett. 124, 055301 (2025)

[4] Roopendra S Rajawat, T. Wang and G. Shvets, arXiv:2209.12748v1(2022)

[5] Roopendra S Rajwat and G. Shvets, in preparation (2025)

[6] Y. Sakawa et al, Phys. Fluids B 5(6), June 1993