AstroGK: Astrophysical gyrokinetics code
Journal of Computational Physics Elsevier 229:24 (2010) 9347-9372
Transport bifurcation in a rotating tokamak plasma.
Physical review letters 105:21 (2010) 215003
Abstract:
The effect of flow shear on turbulent transport in tokamaks is studied numerically in the experimentally relevant limit of zero magnetic shear. It is found that the plasma is linearly stable for all nonzero flow shear values, but that subcritical turbulence can be sustained nonlinearly at a wide range of temperature gradients. Flow shear increases the nonlinear temperature gradient threshold for turbulence but also increases the sensitivity of the heat flux to changes in the temperature gradient, except over a small range near the threshold where the sensitivity is decreased. A bifurcation in the equilibrium gradients is found: for a given input of heat, it is possible, by varying the applied torque, to trigger a transition to significantly higher temperature and flow gradients.Gyrokinetic simulation of entropy cascade in two-dimensional electrostatic turbulence
Journal of Plasma and Fusion Research SERIES Japan Society of Plasma Science and Fusion Research 9 (2010) 509-516
Abstract:
Two-dimensional electrostatic turbulence in magnetized weakly-collisional plasmas exhibits a cascade of entropy in phase space [Phys. Rev. Lett. 103, 015003 (2009)]. At scales smaller than the gyroradius, this cascade is characterized by the dimensionless ratio D of the collision time to the eddy turnover time measured at the scale of the thermal Larmor radius. When D >> 1, a broad spectrum of fluctuations at sub-Larmor scales is found in both position and velocity space. The distribution function develops structure as a function of v_{perp}, the velocity coordinate perpendicular to the local magnetic field. The cascade shows a local-scale nonlinear interaction in both position and velocity spaces, and Kolmogorov's scaling theory can be extended into phase space.Direct multiscale coupling of a transport code to gyrokinetic turbulence codesa)
Physics of Plasmas AIP Publishing 17:5 (2010) 056109
Resolving velocity space dynamics in continuum gyrokinetics
Physics of Plasmas AIP Publishing 17:3 (2010) 032106