Abstract:

TIFF : Turbulence in Full-f and Full-k

Wider research context / theoretical framework:

This project is concerned with theory and simulation of turbulence, transport and structure formation in magnetized plasmas, with a focus on modelling the edge and scrape-off layer region of tokamak and stellarator fusion plasmas. We specifically further develop and apply advanced gyrofluid models.

Hypotheses / research questions / objectives:

In the edge and scrape-off layer (SOL) of magnetized fusion plasmas (but also in many other laboratory, space or astrophysical plasmas), the amplitudes of turbulent fluctuations and nonlinear structures can often not be regarded as small compared to the background or average plasma quantities. This necessitates the use of non-Boussinesq methods, which for gyrokinetic and gyrofluid models require the evolution of the full distribution function ("full-f") instead of small fluctuations ("delta-f"). Present consistent full-f gyrokinetic and gyrofluid polarization models usually employ some long-wavelength (low-k) approximation, whereas delta-f models use arbitrary wavelength (full-k) forms. Comparisons between low-k and full-k delta-f simulations show considerable differences, which question the applicability of low-k full-f models. In this project we develop, implement, test and apply a novel energetically consistent full-k / full-f gyrofluid code.

Approach / methods:

We have recently proposed a novel energetically consistent full-k / full-f model (arXiv:1907.13439, submitted for publication). In the following project, this model shall be implemented into one or both of our existing full-f (so far low-k) gyrofluid turbulence codes, tested, if necessary improved, and cross-verified against the respective known limits (full-k delta-f, or low-k full-f). The final aim is a consistent full-k / full-f gyrofluid turbulence code applicable to the edge and SOL regions of tokamak and fusions plasmas, which can be cross-verified with complementary gyrokinetic or fluid models, and applied to experimental edge turbulence and transport modelling.

Level of originality / innovation:

While several large groups presently develop full-f (low-k) gyrokinetic codes, we so far have uniquely studied corresponding highly efficient full-f gyrofluid (low-k) models. Our proposed extension to full-k will not only be a large step towards quantitatively more reliable gyrofluid turbulence modelling, but can also help the gyrokinetics community in assessment of the necessity and further development of full-k / full-f gyrokinetic implementations.