Self-generated vortex flows in a tokamak magnetic island with a background flow

[摘要] We present a gyrokinetic theory of self-generated E×B vortex flows in a magnetic island in a collisionless tokamak plasma with a background vortex flow. We find that the long-term evolution of the self-generated vortex flows can be classified into two regimes by the background vortex flow potential Φ, with an asymptotic criterion given by ePhi_mathrm{cr}/T = epsilon w/r , whereTis temperature, ε is the inverse aspect ratio andris the radial coordinate. We find that the background vortex flow above the criterion significantly weakens the toroidal precession-induced long-term damping and structure change of the self-generated vortex flows. That is, the finite background vortex flow is beneficial to maintain the self-generated vortex flows, favorable to an internal transport barrier formation. Our result indicates that the island boundary region is a prominent location for triggering the transition to an enhanced confinement state of the magnetic island.

[关键词] gyrokinetics;tokamak;magnetic island;vortex flow;turbulence;self-generation;transport barrier