An ELMy ASDEX Upgrade plasma equilibrium is reconstructed takinginto account the bootstrap current. The peeling mode stability of theequilibrium is numerically analysed using the GATO [1] code, and it is foundthat the bootstrap current can drive the plasma peeling mode unstable. Ahigh-n ballooning mode stability analysis of the equilibria revealed that,while destabilizing the peeling modes, the bootstrap current has a stabilizingeffect on the ballooning modes. A combination of these two instabilities is apossible explanation for the type I ELM phenomenon. A triangularity scanshowed that increasing triangularity stabilizes the peeling modes and canproduce ELM-free periods observed in the experiments.
MHD stability analysis of small ELM regimes in JET