Editing Plasma stability (section)

=== Resistive instabilities ===
Resistive instabilities are an issue for all magnetic configurations, since the onset can occur at beta values well below the ideal limit. The stability of neoclassical tearing modes (NTM) is a key issue for magnetic configurations with a strong [[bootstrap current]]. The NTM is a metastable mode; in certain plasma configurations, a sufficiently large deformation of the bootstrap current produced by a “seed island” can contribute to the growth of the island. The NTM is already an important performance-limiting factor in many tokamak experiments, leading to degraded confinement or disruption. Although the basic mechanism is well established, the capability to predict the onset in present and future devices requires better understanding of the damping mechanisms which determine the threshold island size, and of the [[mode coupling]] by which other instabilities (such as sawteeth in tokamaks) can generate seed islands. [[Resistive Ballooning Mode]], similar to ideal ballooning, but with finite resistivity taken into consideration, provides another example of a resistive instability.