Interaction between static magnetic islands and interchange modes in a straight heliotron plasma with high resistivity

Fundamental mechanism of the nonlinear interaction between static magnetic islands generated by an external field and a resistive interchange mode is investigated in a straight heliotron plasma with high resistivity by using a numerical method based on the reduced magnetohydrodynamics equations. The behavior of the magnetic islands is examined at the steady state after the nonlinear saturation of the interchange mode. The width and the phase of the magnetic islands are changed by the mode evolution. These changes are almost determined by the linear combination of the two perturbed poloidal magnetic fluxes, the flux imposed externally and the flux attributed to the interchange mode, in spite of the fact that the changes result from the nonlinear process. It is also obtained that the amount of the local change of the pressure at the resonant surface in the saturation state depends on the phase of the static magnetic islands.