Bienvenue - Laboratoire Jacques-Louis Lions

Séance du 2 Décembre 2015 à 11h00

SUMIRE KOBAYASHI

LPP & Ecole Polytechnique

Titre :

The predator-prey interaction between zonal flows and turbulence in gyrokinetic simulations.

Résumé :

The zonal flow generation within turbulence is ubiquitous in 2D fluid and plasma turbulence, for example, as seen in the atmosphere of Jupiter and Saturn, Earth’s jet streams, and in various magnetically confined fusion experiments. One of the biggest challenges in magnetic fusion is the loss of plasma and heat due to turbulent transport. Because of its ability to suppress turbulence, recent studies in magnetic fusion community have focused on untangling the dynamics of zonal flow and turbulence. However, the detailed mechanisms are still not very well understood. During this talk, I will discuss the predator-prey-like dynamics between zonal flows (predator) and turbulence (prey) observed in gyrokinetic simulations. In particular, we show the emergence of characteristic turbulent spectrum in the presence of zonal flows, which is compared with a simple theoretical model. Also, we demonstrate some results of dynamical fitting between nonlinear gyrokinetic simulations and a simple Lotka-Volterra type predator-prey model. This type of analysis allows us to extract the model coefficients that are usually difficult to measure. The result might gives us some clues about the underlying physics, as well as some potential of applying such analysis in actual experimental data.