Three wave coupling in gyrokinetic multi-scale interaction

Maeyama, Shinya*; Watanabe, Tomohiko*; Idomura, Yasuhiro   ; Nakata, Motoki*; Ishizawa, Akihiro*; Nunami, Masanori*

In order to analyze multi-scale interactions in fine scale gyrokinetic simulations covering both ion and electron scales, we develop a fluid moment based analysis method for three wave coupling. In analyzing three wave coupling of gyrokinetic equations, one needs to keep interactions of five dimensional (5D) distribution functions. However, it is prohibitive to store such massive data. In this talk, we propose an approximate analysis method based on 3D fluid moments, which are reduced by integrating 5D distribution functions over velocity space, and discuss its accuracy. By applying this method, we found a new damping mechanism of ion scale zonal flows due to electron scale turbulence.