Abstract
The behavior of non-linear tearing modes and the plasma flows around magnetic islands is studied numerically in a cylindrical geometry using the method of reduced magneto-hydro-dynamic simulation. The results show that the single tearing mode (STM) becomes stable in a short time. The magnetic islands of double tearing modes (DTMs) first develop to a sufficiently large scale and then couple together when entering the non-linear phase. It is also shown that, before the non-linear growth stage, the perturbed kinetic energy and magnetic energy of both the STM and DTM have a process from different signs to constant positive values. For the STM island and plasma flow, it is demonstrated that the shear flow is formed on both sides of the islands and the poloidal flow velocity around the O-point is larger than that around the X-point. For the DTM island and plasma flow, we found that the peak of the poloidal flow velocity is mainly distributed at the O-point edge and the X-point of the magnetic island and the plasma flow velocities at the magnetic island edges are opposite. In addition, the process of plasma flow accompanying the nonlinear evolution of tearing modes is also presented.
Highlights
Advanced tokamak operations have been studied adequately because of their higher bootstrap current fraction and the significant transport improvement obtained with reversed magnetic shear
For the double tearing modes (DTMs) island and plasma flow, we found that the peak of the poloidal flow velocity is mainly distributed at the O-point edge and the X-point of the magnetic island and the plasma flow velocities at the magnetic island edges are opposite
We numerically investigate the nonlinear behavior of single tearing modes (STMs), the DTM, and the plasma flows around the magnetic islands based on the reduced MHD model in a cylindrical geometry
Summary
Advanced tokamak operations have been studied adequately because of their higher bootstrap current fraction and the significant transport improvement obtained with reversed magnetic shear. In the study of tearing modes, in terms of the linear and nonlinear behavior of the DTM under the cylindrical geometry, it is found that the distance between the two rational planes has a great influence on the evolution of the magnetic island.. 14–16 studied a MHD flow driven by the energy of the magnetic field released during the evolution of the tearing mode They mainly analyzed the characteristics of the tearing mode under the influence of anomalous electron viscosity and plasma resistance in the slab geometry and gave the scaling relationship of the linear growth rate of the tearing mode. We numerically investigate the nonlinear behavior of single tearing modes (STMs), the DTM, and the plasma flows around the magnetic islands based on the reduced MHD model in a cylindrical geometry.
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