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(THP2/11) Improved Theory of Forced Magnetic Reconnection Due to Error Field and its Application to Seed Island Formation for NTM

A. Ishizawa¹⁾, S. Tokuda²⁾, M. Wakatani^1)
 
1) Kyoto University, Kyoto, Japan
²⁾ Japan Atomic Energy Research Institute, Ibaraki, Japan

Abstract.  A seed island is required for destabilizing the neo-classical tearing mode (NTM), which degrades confinement in long sustained, high-confinement, high beta plasmas. The seed island formation due to an MHD event, such as a sawtooth crash, is investigated by applying the improved boundary layer theory of forced magnetic reconnection. This improved theory introduces the non-constant-$\psi$ matching and reveals the complicated feature of the reconnection described by two reconnected fluxes. In the initial evolution, these reconnected fluxes grow on the time scale including the ideal time scale, typical time scale of the MHD event and the time scale of resistive kink mode. The surface current is negative, $\Delta{^\prime}$(t) < 0, to be consistent with the NTM theory. The theory also yields an integral equation which includes the typical time scale of the resistive kink mode, and allows us to investigate the time evolution of the seed island at t $\approx$ $\tau_{A}^{}$S^1/3.

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