Scalings of strongly coupled collisionless q = 2 triple tearing modes in a tokamak plasma

Journal Article · Fri Apr 15 00:00:00 EDT 2011 · Physics of Plasmas

DOI:https://doi.org/10.1063/1.3581055· OSTI ID:21537646

Lai, Wei; Zhengxiong, Wang; Dongmei, Fan; Feng, Wang; Yue, Liu ^[1]

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1. Key Laboratory of Materials Modification by Beams of the Ministry of Education, School of Physics and Optoelectronic Technology, Dalian University of Technology, Dalian 116024 (China)

Within the framework of a reduced collisionless magnetohydrodynamics (MHD) model containing the effects of electron inertia and electron pressure gradient, scaling laws of the strongly coupled collisionless q=2 triple tearing instabilities with broad linear spectra in a tokamak plasma are studied numerically. It is found that as the poloidal mode number m increases, the scaling power laws of the linear growth rate of triple tearing modes (TTMs) on S{sub Hp}, d{sub e}, and {rho}{sub s} change gradually from the strongly coupled tearing mode scalings to the standard single tearing mode (STM) scalings, where S{sub Hp} is the magnetic Reynolds number, d{sub e} is the electron inertial skin depth, and {rho}{sub s} is the ion sound gyroradius. For example, d{sub e}-scaling of the linear growth rate {gamma}{approx}d{sub e}{sup {alpha}}{sub d} changes gradually from {gamma}{approx}d{sub e}{sup 1} to {gamma}{approx}d{sub e}{sup 3} as the m number increases in the case of {rho}{sub s}<<d{sub e}, while {rho}{sub s}-scaling {gamma}{approx}d{sub e}{sup {alpha}}{sub {rho}} shifts gradually from {gamma}{approx}{rho}{sub s}{sup 2/3} to {gamma}{approx}{rho}{sub s}{sup 1} as m increases in the case of d{sub e}<<{rho}{sub s}. Furthermore, it is observed that the increase of {rho}{sub s} gradually weakens the dependence on d{sub e} in both large and small {Delta}' regimes, such as, {approx}d{sub e}{sup 1{yields}{approx}}d{sub e}{sup 1/3} in the large {Delta}' regime, where {Delta}' is the linear instability parameter of tearing modes. The numerical results about the scaling laws are validated by the previous relevant analytical theories in terms of the similarity of physical characteristics in the same {Delta}' regime. In addition, the effects of d{sub e} and {rho}{sub s} on the spectrum structures of the unstable TTMs are discussed. Finally, the spatial characteristics of the eigenmode structures for different mode numbers are analyzed in detail. It is interestingly found that the structure of the most unstable eigenmode of the TTMs is quite similar to the eigenmode structure of a standard double tearing mode (DTM).

• OSTI ID: 21537646
• Journal Information: Physics of Plasmas, Vol. 18, Issue 4; Other Information: DOI: 10.1063/1.3581055; (c) 2011 American Institute of Physics; ISSN 1070-664X
• Country of Publication: United States
• Language: English

Related Subjects

70 PLASMA PHYSICS AND FUSION TECHNOLOGY
INSTABILITY GROWTH RATES
MAGNETOHYDRODYNAMICS
PLASMA SIMULATION
PRESSURE GRADIENTS
SCALING
SCALING LAWS
TEARING INSTABILITY
TOKAMAK DEVICES
CLOSED PLASMA DEVICES
FLUID MECHANICS
HYDRODYNAMICS
INSTABILITY
MECHANICS
PLASMA INSTABILITY
PLASMA MACROINSTABILITIES
SIMULATION
THERMONUCLEAR DEVICES