Fundamentals of Magnetic Island Theory in Tokamaks

Tearing modes are magnetohydrodynamic (MHD) instabilities that often limit fusion plasma performance in tokamaks. As the name suggests, tearing modes tear and reconnect magnetic field lines, in the process converting nested toroidal flux surfaces into helical magnetic islands. Such islands degrade plasma confinement because heat and particles are able to travel radially from one side of an island to another by flowing along magnetic field lines, which is a relatively fast process, instead of having to diffuse across magnetic flux surfaces, which is a relatively slow process. [first paragraph from extended abstract]