Cross-scale Dynamo Action in Multiscale Plasma Turbulence

The interplay mechanism between electromagnetic (EM) and electrostatic (ES) turbulence is explored using direct gyrofluid simulations of mixed resistive magnetohydrodynamic (MHD) and ion-scale microinstability. With an elucidation based on a minimal model, we propose a new concept of cross-scale dynamo action induced by microturbulence as the mechanism responsible for the interaction between multiscale ES and EM turbulence. The dynamo appears as a novel magnetic island seesaw oscillation pivoting around the singular surface. This island seesaw mechanism may be applicable to relaxation of mode locking in tokamaks to mitigate major disruptions, suggesting a promising nonlinear approach to plasma control.