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Author(s):
K. Watanabe, T. Sato and Y. Nakayama
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Title:
Current-profile Flattening and Hot Core Shift due to the Nonlinear Development of Resistive Kink Mode
Date of publication:
Oct. 1994
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Key words:
tokamak, current profile, computer simulation, magnetohydrodynamics, magnetic reconnection
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Abstract:
A new and interesting phenomenon showing that the toroidal current profile for the n=0 mode, which at first exhibits a peak due to ohmic heating and later flattens around the magnetic axis, is obtained through a compressible resistive MHD simulation in a fully 3-D toroidal geometry. We conclude through a detailed analysis that the current flattening is caused by the strong excitation of a nonlinear resistive kink mode. The time-scale of the current profile flattening is of the order of the MHD time-scale. When the current profile is largely flattened, the plasma dynamic pressure due to the strongly excited kink mode pushes the hot core plasma in the radial kink flow direction and the hot core starts deviating from the magnetic surface because of the plasma compressibility and the dynamic pressure. Since the flattening of a current profile weakens the shear effect of the poloidal magnetic field in the q < 1 region where the resistive kink mode is growing , the poloidal magnetic field reconnection is driven by the strong kink flow and leads to complete destruction of the magnetic surface within the q=1 rational surface (minor disruption), and the poloidal magnetic field configuration recovers to an axi-symmetric profile. The effect of the thermal conduction on the evolution of such a process is also discussed.
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