Interaction of tearing modes with external structures in cylindrical geometry (plasma)
Interaction of tearing modes with external structures in cylindrical geometry (plasma)
复制标题
DOI：
10.1088/0029-5515/33/7/i08
复制
发表时间：
1993-07
期刊：
影响因子：
3.3
通讯作者：
R. Fitzpatrick
中科院分区：
文献类型：
--
作者：
R. Fitzpatrick
建立了圆柱几何中撕裂模相互作用研究的基本理论框架。结合电磁信息和流体流动信息，得到了一组描述等离子体中各模式振幅和相位耦合演化的方程。以两种相互作用为例进行了详细的研究。考虑的第一个例子是旋转磁岛与电阻壁相互作用的减速。在一定条件下，得到了分岔稳态解，使得系统随着相互作用强度的逐渐增加，从高旋转状态突然不可逆地转变为低旋转状态，反之亦然。第二个考虑的例子是旋转撕裂模式与静态外部磁扰动的相互作用。一般来说，旋转岛在一定程度上由于相互作用而稳定，而锁定岛则是不稳定的。事实上，一个足够小的饱和宽度的旋转岛是可以完全稳定的。然而，一旦孤岛宽度变得太大，常规模式锁定就会在完全稳定之前发生。与撕裂稳定等离子体的相互作用最初会引起体等离子体旋转的改变，在合理表面引起的磁重联很小。然而，一旦超过临界扰动场强，等离子体的旋转就会突然发生变化，因为在没有旋转磁前体的情况下，在理性表面会产生一个锁岛。这些结果对典型的欧姆加热托卡马克的意义进行了评价。在大型托卡马克中，相对缓慢的模式旋转使得这种设备对错误场诱导的锁定模式特别敏感，并且由于壁相互作用而导致模式旋转崩溃
A basic theoretical framework is developed for the investigation of tearing mode interactions in cylindrical geometry. A set of equations describing the coupled evolution of the amplitude and phase of each mode in the plasma is obtained by combining electromagnetic and fluid flow information. Two interactions are investigated in detail as examples. The first example considered is the slowing down of a rotating magnetic island interacting with a resistive wall. Under certain conditions bifurcated steady state solutions are obtained, allowing the system to make sudden irreversible transitions from high rotation to low rotation states as the interaction strength is gradually increased, and vice versa. The second example considered is the interaction of a rotating tearing mode with a static external magnetic perturbation. In general, a rotating island is stabilized to some extent by the interaction, whereas a locked island is destabilized. In fact, a rotating island of sufficiently small saturated width can be completely stabilized. However, once the island width becomes too large, conventional mode locking occurs prior to complete stabilization. The interaction with a tearing-stable plasma initially gives rise to a modification of the bulk plasma rotation, with little magnetic reconnection induced at the rational surface. However, once a critical perturbation field strength is exceeded, there is a sudden change in the plasma rotation as a locked island is induced at the rational surface, with no rotating magnetic precursor. The implications of these results for typical ohmically heated tokamaks are evaluated. The comparatively slow mode rotation in large tokamaks renders such devices particularly sensitive to error-field induced locked modes, and the collapse of mode rotation due to wall interactions