F. Merz

The global version of the gyrokinetic turbulence code GENE

The understanding and prediction of transport due to plasma microturbulence is a key open problem in modern plasma physics, and a grand challenge for fusion energy research. Ab initio simulations of such small-scale, low-frequency turbulence are to be based on the gyrokinetic equations, a set of nonlinear integro-differential equations in reduced (five-dimensional) phase space. In the present paper, the extension of the well-established and widely used gyrokinetic code GENE [F. Jenko, W. Dorland, M. Kotschenreuther, B.N. Rogers, Electron temperature gradient driven turbulence, Phys. Plasmas 7 (2000) 1904-1910] from a radially local to a radially global (nonlocal) version is described. The necessary modifications of both the basic equations and the employed numerical methods are detailed, including, e.g., the change from spectral methods to finite difference and interpolation techniques in the radial direction and the implementation of sources and sinks. In addition, code verification studies and benchmarks are presented

Clarifications to the limitations of the s-α equilibrium model for gyrokinetic computations of turbulence

In the context of gyrokinetic flux-tube simulations of microturbulence in magnetized toroidal plasmas, different treatments of the magnetic equilibrium are examined. Considering the Cyclone DIII-D base case parameter set [Dimits et al., Phys. Plasmas 7, 969 (2000)], significant differences in the linear growth rates, the linear and nonlinear critical temperature gradients, and the nonlinear ion heat diffusivities are observed between results obtained using either an

Exceptional points in linear gyrokinetics

s-\alpha

Flux- and gradient-driven global gyrokinetic simulation of tokamak turbulence

or an MHD equilibrium. Similar disagreements have been reported previously [Redd et al., Phys. Plasmas 6, 1162 (1999)]. In this paper it is shown that these differences result primarily from the approximation made in the standard implementation of the

Role of subdominant stable modes in plasma microturbulence

s-\alpha

Nonlinear interplay of TEM and ITG turbulence and its effect on transport

model, in which the straight field line angle is identified to the poloidal angle, leading to inconsistencies of order

Free Energy Cascade in Gyrokinetic Turbulence

\varepsilon

Nonlinear quasisteady state benchmark of global gyrokinetic codes

(

Fluid and gyrokinetic simulations of impurity transport at JET

\varepsilon=a/R

Gyrokinetic turbulence under near-separatrix or nonaxisymmetric conditions

is the inverse aspect ratio,