Göttingen 2025 – wissenschaftliches Programm

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P: Fachverband Plasmaphysik

P 5: Magnetic Confinment Fusion/HEPP III

P 5.3: Vortrag

Dienstag, 1. April 2025, 11:55–12:20, ZHG102

Turbulent magnetic fluctuations in plasma edge — •Kaiyu Zhang, Wladimir Zholobenko, Andreas Stegmeir, and Frank Jenko — Max Planck Institute for Plasma Physics, Garching, Germany

Small magnetic fluctuations are inherently present in a magnetic confinement plasma due to turbulent currents. These fluctuations flutter the background field lines, thereby reshaping the turbulence, which is investigated with GRILLIX, a global full-f fluid turbulence code using a locally field-aligned scheme. This study introduces a real-time high-pass filter to screen the magnetic fluctuations in turbulence, based on which the magnetic flutter effect is implemented. The implementation is verified by the method of manufactured solution and validated in the full-size simulations for the edge and scrap-off layer of Asdex Upgrade tokamak. The magnetic flutter in the drift-Alfvén-wave is found to reduce ExB transports by decreasing the phase shift between potential and density fluctuations, imparting stabilizing factors of 2 in the low confinement conditions and up to 100 in high confinement conditions. These findings establish the flutter stabilization as a fundamental aspect of edge turbulence. In reactor-relevant small edge-localized-modes (ELMs) regimes, the magnetic fluctuations form substantial Maxwell stresses, which flatten the radial electric field and weaken the associated flow shear near the separatrix. This facilitates the growth of the quasi-coherent mode driven by the kinetic-ballooning-mode, ultimately contributing to increased flutter transport of particles, conducive to avoiding Type-I ELMs and alleviating the heat exhaust challenge.

Keywords: magnetic fluctuations; plasma turbulence; magnetic confinement