A kink instability (also known as a kink oscillation or kink mode) is a current-driven plasma instability characterized by transverse displacements of a plasma column's cross-section from its

center of mass In physics, the center of mass of a distribution of mass in space (sometimes referred to as the barycenter or balance point) is the unique point at any given time where the weight function, weighted relative position (vector), position of the d ...

without any change in the characteristics of the plasma. It typically develops in a thin plasma column carrying a strong axial current which exceeds the Kruskal–Shafranov limit and is sometimes known as the Kruskal–Shafranov (kink) instability, named after Martin David Kruskal and Vitaly Shafranov. The kink instability was first widely explored in

fusion power Fusion power is a proposed form of power generation that would generate electricity by using heat from nuclear fusion reactions. In a fusion process, two lighter atomic nuclei combine to form a heavier nucleus, while releasing energy. Devices d ...

machines with Z-pinch configurations in the 1950s. It is one of the common magnetohydrodynamic instability modes which can develop in a pinch plasma and is sometimes referred to as the

m=1

mode. (The other is the

m=0

mode known as the sausage instability.) If a "kink" begins to develop in a column the magnetic forces on the inside of the kink become larger than those on the outside, which leads to growth of the perturbation.Plasma Dictionary
As it develops at fixed areas in the plasma, kinks belong to the class of "absolute plasma instabilities", as opposed to convective processes.

References

Plasma instabilities {{plasma-stub