Bound states in the continuum: from quantum mechanics to nanophotonics

Realistic simulations of electromagnetic turbulence are of crucial importance to understand and predict behavior of burning plasmas before they become experimentally available. Burning plasmas are complex systems with multiple spatial and temporal scales. Electromagnetic turbulence is ubiquitous in such plasmas. It is the basic component of the ``scenery'' involving the fast-particle dynamics, the global Magneto-Hydrodynamical and Alfvenic activity, zonal flows, and transport. The saturation of the electromagnetic turbulence is a consequence of a complex interplay between these components. A single numerical first-principle framework, based on the global gyrokinetic electromagnetic formulation and including self-consistently all parts of the problem, is needed. An approach to this task based on the gyrokinetic particle-in-cell codes will be addressed in the presentation. Electromagnetic simulations are known to be very challenging for the gyrokinetic particle-in-cell codes because of the numerical stability issues related to the cancellation problem [1]. Such simulations are also very time consuming since the fast electron dynamics has to be resolved. We address the numerical stability problem using the pullback mitigation technique [2,3] for the cancellation problem. Very long simulation times normally required when the electron dynamics is resolved are substantially accelerated deploying GPUs. In our talk, we will discuss the challenges and describe results of the global gyrokinetic modelling in the electromagnetic regime. [1] Physics of Plasmas, 24(8):081206, 2017 [2] Physics of Plasmas, 21(9):092110, 2014 [3] Computer Physics Communications, 238:194–202, 2019