Cross-Scale Interactions between Electron and Ion Scale Turbulence in a Tokamak Plasma

Area of Science:

• Plasma Physics
• Fusion Energy Research
• Computational Astrophysics

Background:

• Understanding plasma turbulence is crucial for magnetic confinement fusion energy.
• Previous simulations often used simplified mass ratios, limiting applicability to real-world scenarios.
• The role of electromagnetic effects (characterized by beta) on microinstabilities requires detailed investigation.

Purpose of the Study:

• To perform the first multiscale gyrokinetic turbulence simulations using the real ion-to-electron mass ratio and realistic beta values.
• To elucidate the cross-scale interaction mechanisms between electron-scale and ion-scale turbulence.
• To investigate the impact of finite-beta effects on turbulence and transport.

Main Methods:

• Employed advanced multiscale gyrokinetic turbulence simulations.
• Conducted numerical analysis at both electron and ion scales.
• Utilized direct measurement of nonlinear mode-to-mode coupling to analyze turbulence interactions.

Main Results:

• Ion-scale turbulence was found to suppress electron-scale streamers and dominate both ion and electron heat transport, even with real mass ratios.
• Ion-scale eddies, rather than zonal flows, were identified as the primary mechanism for suppressing electron-scale turbulence.
• Finite-beta effects stabilizing ion-scale modes led to non-negligible electron-scale contributions, enhancing overall ion-scale turbulent transport.

Conclusions:

• Ion-scale turbulence plays a dominant role in heat transport and turbulence suppression in realistic plasma conditions.
• Cross-scale interactions are primarily driven by nonlinear coupling between ion-scale eddies and electron-scale turbulence.
• Electron-scale turbulence can enhance ion-scale transport by damping ion-scale zonal flows, particularly under finite-beta conditions.