Energy dynamics in a simulation of LAPD turbulence

Abstract

Energy dynamics calculations in a 3D fluid simulation of drift wave turbulence in the linear Large Plasma Device (LAPD) [W. Gekelman et al., Rev. Sci. Inst. 62, 2875 (1991)] illuminate processes that drive and dissipate the turbulence. These calculations reveal that a nonlinear instability dominates the injection of energy into the turbulence by overtaking the linear drift wave instability that dominates when fluctuations about the equilibrium are small. The nonlinear instability drives flute-like ($k_{\parallel }=0$) density fluctuations using free energy from the background density gradient. Through nonlinear axial wavenumber transfer to $k_{\parallel }\ne 0$ fluctuations, the nonlinear instability accesses the adiabatic response, which provides the requisite energy transfer channel from density to potential fluctuations as well as the phase shift that causes instability. The turbulence characteristics in the simulations agree remarkably well with experiment. When the nonlinear instability is artificially removed from the system through suppressing $k_{\parallel }=0$ modes, the turbulence develops a coherent frequency spectrum which is inconsistent with experimental data.

References in corpus (5)

• BOUT++: a framework for parallel plasma fluid simulations
• Zero-Turbulence Manifold in a Toroidal Plasma
• Analysis of plasma instabilities and verification of the BOUT code for the Large Plasma Device
• Modeling of plasma turbulence and transport in the Large Plasma Device
• Understanding the sub-critical transition to turbulence in wall flows

Cited by in corpus (10)

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• Dirichlet boundary conditions for arbitrary-shaped boundaries in stellarator-like magnetic fields for the Flux-Coordinate Independent method
• Gyrokinetic Continuum Simulation of Turbulence in Open-Field-Line Plasmas
• Nonlinear instability in simulations of Large Plasma Device turbulence
• Full-F Turbulent Simulation in a Linear Device using a Gyro-Moment Approach
• A Linear Technique to Understand Non-Normal Turbulence Applied to a Magnetized Plasma
• Intrinsic suppression of turbulence in linear plasma devices