Small Scale Magnetic Islands in Collisionless Plasmas

摘要

Several investigations have indicated that skin-size electromagnetic turbulenceis a plausible candidate responsible for anomalous transport in tokamaks. Results are presented from a study of nonlinearly saturated magnetic islands (spontaneous breaking of magnetic symmetry) having a characteristic dimension in the range of the skin depth, taking into account the longitudinal inertia of electrons. The existence of these islands is discussed in terms of a hydrodynamic nonlinear dispersion relation for a nonuniform plasma in a sheared magnetic field. A nonlinear equation to describe the steady-state magnetic island having a characteristic width of the order of skin depth is derived and solved. The anomalous electron thermal diffusivity based on the skin-size magnetic turbulence contains the electron temperature gradient (eta) in the form of 1/2 + 1/eta.