Error-fields can drive magnetic reconnection, resulting in the formation of locked magnetic island chains, in intrinsically tearing-stable plasmas. As has already been
mentioned, locked mode formation is strongly correlated with plasma disruptions. Error-field driven reconnection is strongly suppressed by plasma
rotation at the associated rational surface. However, when the error-field amplitude rises above a certain critical value, the rotation
at the rational surface is suddenly arrested, and error-field driven reconnection proceeds unhindered. This phenomenon is known
as error-field penetration [18,20]. The scenario just outlined has been observed in a number of tokamak experiments [17,32,34,45,53,61,62,65,66]. (See Chapter 7.)
