Effects of magnetic separatrix and pressure pedestal on finite beta external kink–tearing modes

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Abstract
The roles of a magnetic separatrix and of a steep‐edge pressure gradient on finite beta external kink and tearing modes in tokamaks are examined by using a newly developed initial value code. For fixed profiles of current density and pressure, the separatrix is found to have a weak effect on the linear characteristics of the global mode. The presence of a steep pressure gradient at the plasma edge reduces the overall growth rate in a similar fashion for both cases with and without the separatrix.