Role of magnetic shear in large-scale structure formation in electron temperature gradient driven turbulence

Formation of secondary large-scale structures in electron temperature gradient (ETG) driven turbulence is investigated based on modeling analyses and three-dimensional gyrofluid turbulence simulations. What state the system evolves to, zonal flow dominated or streamerlike, depends on the spectral anisotropy of ETG turbulence. The radially elongated turbulent fluctuation tends to excite a zonal flow instability, while the poloidally elongated one favors to enhance the streamer formation. The magnetic shear is identified to play a key role in the structure selection through governing the anisotropy of ETG turbulent structures. (c) 2005 American Institute of Physics.