Simulation of turbulence in tokamak plasma (plasma core is not simulated). (Source: © Nathan Howard, MIT)

Minor fluctuations and eddies that arise in various regions of the magnetically confined plasma and can lead to its cooling. They can be compared to turbulence in a liquid, but are much more complex and complicated due to the presence of charged particles and magnetic fields. Turbulence is a fundamental reason why plasma heating is so difficult because it mixes the warm inner parts of the plasma with the cool outer parts. Heat and energy transport in fusion plasma is partly due to turbulent processes. The origin and development of turbulence in plasma is the subject of intensive research and computer simulations. A number of methods (e.g. reversed magnetic shear) are being developed to suppress, better align or disperse the turbulence in order to reduce energy loss through turbulent transport. The confinement mode, called H-mode, has achieved significant confinement improvements by creating a transport barrier at the edge of the plasma where turbulence is significantly reduced.