Magnetic islands and turbulence

The magnetic islands which arise in a fusion plasma play an exceptionally important role in the behavior of the medium. General analyic relations are derived to describe magnetic islands. These relations are compared with extensive numerical calculations of magnetic lines of force. The model used here reproduces the main features of discharges with internal disruptions very well. This model can be used for a semiempirical generalization of the analytic expressions which results in a very good description of the numerical results. It is also possible to analyze the interaction between islands and the beginning of the turbulent stage in such plasmas