Role of resistivity and viscosity in the excitation of stable m = 0 modes during the RFP sawtooth crash

Visco-resistive magnetohydrodynamic simulations are used to investigate the role of resistivity and viscosity in the reversed field pinch sawtooth crash. Specifically, we examine the temporal behavior of the linearly stable (m, n) = (0, 1) mode. Both volume-averaged dissipation and dissipation level...

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Bibliographic Details
Published in:Physics of plasmas 2018-11, Vol.25 (11)
Main Authors: Futch, A. M., Craig, D., Hesse, R., Jacobson, C. M.
Format: Article
Language:English
Subjects:
CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSICS
Computational fluid dynamics
Computer simulation
Electrical resistivity
Energy dissipation
Energy flow
Flow stability
Fluid flow
Magnetohydrodynamic simulation
Physics
Plasma physics
Toruses
Viscosity
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Summary:Visco-resistive magnetohydrodynamic simulations are used to investigate the role of resistivity and viscosity in the reversed field pinch sawtooth crash. Specifically, we examine the temporal behavior of the linearly stable (m, n) = (0, 1) mode. Both volume-averaged dissipation and dissipation levels in the region near the m = 0 resonance are found to influence characteristic time scales. Increasing resistivity causes the mode rise time, fall time, and total crash duration to decrease, while increasing viscosity has the opposite effect. Examination of energy flow during the sawtooth crash reveals that despite the linear stability of the (0, 1) mode, it receives most of its energy from the mean current profile during the crash rather than from nonlinear interactions with other modes. Resistivity and viscosity do not impact mode behavior directly through dissipative energy loss but rather through modification of the large scale current profile evolution and radial structure of the mode. Computational results are compared to experimental data from the Madison Symmetric Torus and found to largely agree when resistivity and viscosity are similar.
ISSN:1070-664X
1089-7674
DOI:10.1063/1.5054578