Scalings of strongly coupled collisionless q=2 triple tearing modes in a tokamak plasma
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论文类型：期刊论文
发表时间：2011-04-01
发表刊物：PHYSICS OF PLASMAS
卷号：18
期号：4
ISSN号：1070-664X
摘要：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-Hp, d(e), and rho(s) change gradually from the strongly coupled tearing mode scalings to the standard single tearing mode (STM) scalings, where S-Hp is the magnetic Reynolds number, d(e) is the electron inertial skin depth, and rho(s) is the ion sound gyroradius. For example, d(e)-scaling of the linear growth rate gamma similar to d(e)(alpha d) changes gradually from gamma similar to d(e)(1) to gamma similar to d(e)(3) as the m number increases in the case of rho(s) << d(e), while rho(s)-scaling gamma similar to d(e)(alpha rho) shifts gradually from gamma similar to rho(2/3)(s) to gamma similar to rho(1)(s) as m increases in the case of d(e) << rho(s). Furthermore, it is observed that the increase of rho(s) gradually weakens the dependence on d(e) in both large and small Delta' regimes, such as, similar to d(e)(1) -> similar to d(e)(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(e) and rho(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). (C) 2011 American Institute of Physics. [doi:10.1063/1.3581055]
发表时间：2011-04-01