Turbulent Nature of the Quasicontinuous Exhaust Regime for Fusion Plasmas

Abstract: We demonstrate a mechanism for reconciling high confinement with heat exhaust in fusion plasmas. Global fluid turbulence simulations of the Quasicontinuous Exhaust regime in the ASDEX Upgrade tokamak show that a quasi-coherent mode (QCM) causes the pedestal foot to oscillate across the separatrix and eject ballistic blobs into the scrape-off layer (SOL), reproducing not only mean profiles but also fluctuation spectra and mode structure seen in experiments. The QCM is a kinetic ballooning mode that develops an extended radial correlation length via electromagnetic self-organization of turbulence, thereby driving enhanced transport, with Maxwell stress and finite Larmor radius effects mediating the process. The blobs are launched when resistivity excites a secondary mode that originates from the X-point and interacts with QCM. The blob-dominated SOL temperature fall-off is then well decoupled from the pedestal-foot gradient set by the QCM.