Core Perturbations Caused by Edge-Localized Modes (ELMs) in DIII-D

The inward propagation of the perturbations caused by edge-localized modes (ELMs) is studied in DIII-D. ELMs are associated with peeling-ballooning modes in tokamaks, which have eigenfunctions that are localized to the edge and pedestal region, but the core density is seen to respond strongly to each ELM crash. Type-I ELMs are analyzed using various diagnostics (microwave reflectometry, electron cyclotron emission, and soft x-ray). Penetration deep into the core from an ELM crash is observed for type-I ELMs in certain cases. In these cases, the ``hole'' caused by an ELM crash propagates as far as the magnetic axis. The depth of the perturbation is compared to ELM size and the time in-between subsequent ELMs. The time scale that the perturbation is seen to travel in is also analyzed in relation to diffusive or ballistic transport.