Phase dynamics and locking of large-scale modes in edge plasmas

Turbulence is often characterized by energetic couplings between different scales of a flow. However, in the context of turbulence driven transport, such as the case of magnetically confined fusion plasmas typical flow structures are identified by dominant modes and the global turbulent state is approximated by a superposition of linear contributions (waves in general). These theoretical studies consider the amplitudes of the fluctuating quantities but disregard the dynamics of the phases by using the so-called random-phase approximation (RPA) for which the existence of a Chirikov-like criterion for the onset of wave stochasticity is assumed.

It has been observed that the phase dynamic shows significant departure from the well-known RPA assumptions, with phases locking occasionally (but not in the dissipative high-k range). In this work, a combination of theoretical premises and simulation data is used to investigate the features of synchronization of large-scale modes leading to edge-localized modes (ELMs). Specially, this study looks into the dynamic of phase locking in the energy transfers between different scales as ELM cycles appear. The results are presented and a discussion taking into account the phase locking in the statistical closure is put forward.