Hybrid kinetic-MHD simulations of ELMs with fast-ion kinetic effects in the ASDEX Upgrade tokamak

Hybrid kinetic-magnetohydrodynamic (MHD) simulations of edge-localized modes (ELMs) in the ASDEX Upgrade tokamak with the initial value code MEGA are presented in this manuscript and show that, when the fast-ion pressure becomes comparable to the MHD drive, the resulting imbalance between fast-ion and MHD forces increases the mode frequency, reaching values consistent with those observed experimentally in ELM crashes in the presence of fast-ions. First, we provide a detailed description of the numerical setup of MEGA to calculate plasma dynamics at the edge. Subsequently, the MHD module of MEGA is used to simulate the ELM crash without fast-ions, observing the plasma filaments that are ejected from the plasma region, with the consequence of the flattening of the driving sources. Next, systematic scans of the fast-ion parameter space are performed to understand fast-ion effects on ELMs. For core-localized fast-ion distributions, the ELM is unaltered and, after the ELM crash, an energetic particle mode is excited. In the presence of fast-ions at the plasma edge, the ELM crash is characterized by modes that become radially broader and with higher frequencies for increasing fast-ion birth energy.