Excitation of macromagnetohydrodynamic mode due to multiscale interaction in a quasisteady equilibrium formed by a balance between microturbulence and zonal flow
Abstract
This is the first numerical simulation demonstrating that a macromagnetohydrodynamic (macroMHD) mode is excited as a result of multiscale interaction in a quasisteady equilibrium formed by a balance between microturbulence and zonal flow based on a reduced twofluid model. This simulation of a macroMHD mode, a double tearing mode, is accomplished in a reversed shear equilibrium that includes zonal flow and turbulence due to kinetic ballooning modes. In the quasisteady equilibrium, a macroscale fluctuation that has the same helicity as the double tearing mode is a part of the turbulence. After a certain period of time, the macroMHD mode begins to grow. It effectively utilizes free energy of the equilibrium current density gradient and is destabilized by a positive feedback loop between zonal flow suppression and magnetic island growth. Thus, once the macroMHD appears from the quasiequilibrium, it continues to grow steadily. This simulation is more comparable with experimental observations of growing macroMHD activity than earlier MHD simulations starting from linear macroinstabilities in a static equilibrium.
 Authors:
 National Institute for Fusion Science, Toki 5095292 (Japan)
 Publication Date:
 OSTI Identifier:
 20974908
 Resource Type:
 Journal Article
 Resource Relation:
 Journal Name: Physics of Plasmas; Journal Volume: 14; Journal Issue: 4; Other Information: DOI: 10.1063/1.2716669; (c) 2007 American Institute of Physics; Country of input: International Atomic Energy Agency (IAEA)
 Country of Publication:
 United States
 Language:
 English
 Subject:
 70 PLASMA PHYSICS AND FUSION TECHNOLOGY; BALLOONING INSTABILITY; CURRENT DENSITY; EQUILIBRIUM; EQUILIBRIUM PLASMA; EXCITATION; FLUCTUATIONS; FREE ENERGY; INTERACTIONS; MAGNETIC ISLANDS; MAGNETOHYDRODYNAMICS; PLASMA SIMULATION; REVERSED SHEAR; TEARING INSTABILITY; TURBULENCE
Citation Formats
Ishizawa, A., and Nakajima, N. Excitation of macromagnetohydrodynamic mode due to multiscale interaction in a quasisteady equilibrium formed by a balance between microturbulence and zonal flow. United States: N. p., 2007.
Web. doi:10.1063/1.2716669.
Ishizawa, A., & Nakajima, N. Excitation of macromagnetohydrodynamic mode due to multiscale interaction in a quasisteady equilibrium formed by a balance between microturbulence and zonal flow. United States. doi:10.1063/1.2716669.
Ishizawa, A., and Nakajima, N. Sun .
"Excitation of macromagnetohydrodynamic mode due to multiscale interaction in a quasisteady equilibrium formed by a balance between microturbulence and zonal flow". United States.
doi:10.1063/1.2716669.
@article{osti_20974908,
title = {Excitation of macromagnetohydrodynamic mode due to multiscale interaction in a quasisteady equilibrium formed by a balance between microturbulence and zonal flow},
author = {Ishizawa, A. and Nakajima, N.},
abstractNote = {This is the first numerical simulation demonstrating that a macromagnetohydrodynamic (macroMHD) mode is excited as a result of multiscale interaction in a quasisteady equilibrium formed by a balance between microturbulence and zonal flow based on a reduced twofluid model. This simulation of a macroMHD mode, a double tearing mode, is accomplished in a reversed shear equilibrium that includes zonal flow and turbulence due to kinetic ballooning modes. In the quasisteady equilibrium, a macroscale fluctuation that has the same helicity as the double tearing mode is a part of the turbulence. After a certain period of time, the macroMHD mode begins to grow. It effectively utilizes free energy of the equilibrium current density gradient and is destabilized by a positive feedback loop between zonal flow suppression and magnetic island growth. Thus, once the macroMHD appears from the quasiequilibrium, it continues to grow steadily. This simulation is more comparable with experimental observations of growing macroMHD activity than earlier MHD simulations starting from linear macroinstabilities in a static equilibrium.},
doi = {10.1063/1.2716669},
journal = {Physics of Plasmas},
number = 4,
volume = 14,
place = {United States},
year = {Sun Apr 15 00:00:00 EDT 2007},
month = {Sun Apr 15 00:00:00 EDT 2007}
}

The effect of zonal flow shear on the double tearing mode is investigated by solving the linear reduced twofluid equations for the equilibrium including zonal flow. The zonal flow caused by microturbulence is obtained from nonlinear simulation results presented by A. Ishizawa and N. Nakajima [Phys. Plasmas 14, 040702 (2007)]. There is no clear evidence that could indicate whether the double tearing mode is stabilized or destabilized by the zonal flow.

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