Sawtooth instability in tokamak plasmas

The Sawtooth instability is a familiar feature in Tokamak plasmas. It appea rs as a regularly recurring reorganisation of the core plasma A brief surve y of the experimental observations on many Tokamaks is presented. A qualita tive description of the relevant theoretical ideas and of how they have evo lved from early magnetic reconnection models in response to increasingly de tailed experimental data, is also presented.