Evidence of Nonlinear Coupling in the Edge Harmonic Oscillation Sustaining Quiescent High Confinement in a Tokamak Plasma
Phys. Rev. Lett. 136, 185101 – Published 6 May, 2026
DOI: https://doi.org/10.1103/z7j9-1t1m
Abstract
In a tokamak plasma, we measure nonlinear coupling between harmonics comprising a saturated edge oscillation, as predicted by nonlinear magnetohydrodynamic simulations. The coherent structure formed by this coupling suppresses bursty edge-localized modes that cause energy and particle loss. We also measure nonlinear coupling of the edge harmonic oscillation to core-resonant magnetic tearing modes. When tearing modes are present, the edge oscillation harmonics decouple, and edge-localized modes return. We conclude that nonlinear interaction with tearing modes interrupts the formation of the edge harmonic oscillation.
