Interactions between MHD-scale tearing modes (TMs) and ion-gyroradius-scale trapped-electron modes (TEMs) in a fusion plasma are simulated with global gyrokinetics, using a consistent set of fixed equilibrium profiles. Unstable core TMs nonlinearly couple and transfer energy to smaller-scale stable TMs near the edge, where TEMs are present. Magnetic stochasticity from these edge TMs erodes TEM-generated zonal flows near the edge rational surfaces, leading to strongly increased electrostatic flux. This interaction of macro- and microscale modes suggests it may be possible to control microturbulence through current-profile modifications.

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• Drift waves
• Magnetic confinement fusion
• Magnetic reconnection
• Plasma transport
• Plasma turbulence
• Tearing instability