Semianalytical calculation of the zonal-flow oscillation frequency in stellarators

Abstract

Due to their capability to reduce turbulent transport in magnetized plasmas, understanding the dynamics of zonal flows is an important problem in the fusion programme. Since the pioneering work by Rosenbluth and Hinton in axisymmetric tokamaks, it is known that studying the linear and collisionless relaxation of zonal flow perturbations gives valuable information and physical insight. Recently, the problem has been investigated in stellarators and it has been found that in these devices the relaxation process exhibits a characteristic feature: a damped oscillation. The frequency of this oscillation might be a relevant parameter in the regulation of turbulent transport, and therefore its efficient and accurate calculation is important. Although an analytical expression can be derived for the frequency, its numerical evaluation is not simple and has not been exploited systematically so far. Here, a numerical method for its evaluation is considered, and the results are compared with those obtained by calculating the frequency from gyrokinetic simulations. This "semianalytical" approach for the determination of the zonal-flow frequency reveals accurate and faster than the one based on gyrokinetic simulations.

arXiv comment30 pages, 14 figures

References in corpus (3)

• The effect of tangential drifts on neoclassical transport in stellarators close to omnigeneity
• Stellarators close to quasisymmetry
• Residual zonal flows in tokamaks and stellarators at arbitrary wavelengths

Cited by in corpus (8)

• Nonlinear gyrokinetic PIC simulations in stellarators with the code EUTERPE
• Electrostatic gyrokinetic simulations in Wendelstein 7-X geometry: benchmark between the codes stella and GENE
• Comparison of local and global gyrokinetic calculations of collisionless zonal flow damping in quasi-symmetric stellarators
• Oscillatory relaxation of zonal flows in a multi-species stellarator plasma
• The residual flow in well-optimized stellarators
• Collisionless zonal-flow dynamics in quasisymmetric stellarators
• The zonal-flow residual does not tend to zero in the limit of small mirror ratio
• Gyrokinetic simulations in stellarators using different computational domains