The nonlinear resistive-kink mode in the low resistivity plasma in tokamak is investigated through the three-dimensional, toroidal, and nonlinear Hall-MHD code CLT. It is found that, without the two-fluid effect and the toroidal flow, the system can evolve into a steady-state with the saturated main m/n = 1/1 magnetic island and the co-existing large secondary island. The main m/n = 1/1 magnetic island cannot push the hot core plasma out of the q = 1 surface as it does in Kadomstev's model, and the reconnection is incomplete. However, with the two-fluid effect or the toroidal flow, the nonlinear behaviors of the resistive-kink mode could be essentially different. The two-fluid effect and the toroidal flow can break the symmetry during the plasmoid formation, which destroys the balance between the main m/n = 1/1 magnetic island and the large secondary island. The large secondary island is then merged into the main m/n = 1/1 island. After that, the main m/n = 1/1 island finally occupies the whole mix region, and all magnetic flux in the mix region is reconnected. A similar simulation study has been done in periodic cylindrical geometry (Günter et al 2015 Plasma Phys. Control. Fusion57 014017), while our work is done in tokamak toroidal geometry. The toroidal effect has also been investigated, and we find that the widths of the main 1/1 island and the secondary island slightly increase with increasing aspect ratios.
低抵抗率プラズマ中のトカマクにおける非線形抵抗性キンクモードを、3次元トロイダル非線形Hall-MHDコードCLTを用いて調べた。二流体効果とトロイダル流がない場合、系は飽和した主m/n = 1/1磁気島と共存する大きな二次島を伴う定常状態へと発展し得ることが見出された。主m/n = 1/1磁気島は、Kadomtsevモデルのように高温コアプラズマをq = 1面の外へ押し出すことができず、リコネクションは不完全である。しかし、二流体効果またはトロイダル流がある場合、抵抗性キンクモードの非線形挙動は本質的に異なり得る。二流体効果とトロイダル流はプラズモイド形成中の対称性を破ることができ、これにより主m/n = 1/1磁気島と大きな二次島の間のバランスが崩れる。その後、大きな二次島は主m/n = 1/1島に合体する。その後、主m/n = 1/1島は最終的に混合領域全体を占め、混合領域内のすべての磁束がリコネクションされる。同様のシミュレーション研究が周期的円柱幾何学で行われているが(Günter et al 2015 Plasma Phys. Control. Fusion57 014017)、我々の研究はトカマクトロイダル幾何学で行われている。トロイダル効果も調べられており、主1/1島と二次島の幅はアスペクト比の増加とともにわずかに増加することが見出された。