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The development of small- and no-ELM regimes for ITER is a high prioritytopic due to the risks associated to type-I ELMs. By considering non-linearextended MHD simulations of the ASDEX Upgrade tokamak with the JOREK code, weprobe a regime that avoids type-I ELMs completely provided that the separatrixdensity is high enough. The dynamics of the pedestal in this regime areobserved to be qualitatively similar to the so-called quasi-continuous exhaust(QCE) regime in several ways. Repetitive type-I ELMs are substituted by roughlyconstant levels of outwards transport caused by peeling-ballooning modes (withdominant ballooning characteristics) which are localised in the last 5\% of theconfined region (in normalised poloidal flux). The simulated low triangularityplasma transitions to a type-I ELMy H-mode if the separatrix density issufficiently reduced or if the input heating power is sufficiently increased.The stabilising factors that play a role in the suppression of the small ELMsare also investigated by analysing the simulations, and the importance ofincluding diamagnetic effects in the simulations is highlighted. By consideringa scan in the pedestal resistivity and by measuring the poloidal velocity ofthe modes (and comparing to theoretical estimates for ideal and resistivemodes), we identify the underlying instabilities as resistivepeeling-ballooning modes. Decreasing the resistivity belowexperimentally-relevant conditions (i.e., going towards ideal MHD), thepeeling-ballooning modes that constrain the pedestal below the type-I ELMstability boundary display sharply decreasing growth rates.

MHD simulations of small ELMs at low triangularity in ASDEX Upgrade