Nonlinear instability in simulations of Large Plasma Device turbulence

Abstract

Several simulations of turbulence in the Large Plasma Device (LAPD) [W. Gekelman et al., Rev. Sci. Inst. 62, 2875 (1991)] are energetically analyzed and compared with each other and with the experiment. The simulations use the same model, but different axial boundary conditions. They employ either periodic, zero-value, zero-derivative, or sheath axial boundaries. The linear stability physics is different between the scenarios because the various boundary conditions allow the drift wave instability to access different axial structures, and the sheath boundary simulation contains a conducting wall mode instability which is just as unstable as the drift waves. Nevertheless, the turbulence in all the simulations is relatively similar because it is primarily driven by a robust nonlinear instability that is the same for all cases. The nonlinear instability preferentially drives $k_{\parallel }=0$ potential energy fluctuations, which then three-wave couple to $k_{\parallel }\ne 0$ potential energy fluctuations in order to access the adiabatic response to transfer their energy to kinetic energy fluctuations. The turbulence self-organizes to drive this nonlinear instability, which destroys the linear eigenmode structures, making the linear instabilities ineffective.

References in corpus (5)

• Modification of turbulent transport with continuous variation of flow shear in the Large Plasma Device
• Zero-Turbulence Manifold in a Toroidal Plasma
• Energy dynamics in a simulation of LAPD turbulence
• Analysis of plasma instabilities and verification of the BOUT code for the Large Plasma Device
• Understanding the sub-critical transition to turbulence in wall flows

Cited by in corpus (4)

• Gyrokinetic continuum simulation of turbulence in a straight open-field-line plasma
• A Linear Technique to Understand Non-Normal Turbulence Applied to a Magnetized Plasma
• On the nonlinear stability of a quasi-two-dimensional drift kinetic model for ion temperature gradient turbulence
• Turbulence and transport in mirror geometries in the Large Plasma Device