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arXiv physics/0410178physics.plasm-ph
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磁曲率驱动的三维Rayleigh Taylor不稳定性的非线性饱和

Nonlinear saturation of magnetic curvature driven Rayleigh Taylor instability in three dimensions

Abhijit Sen, Amita Das, Predhiman Kaw, S. Benkadda, P. Beyer

摘要:

我们给出了三维流体模拟结果的时间演化和非线性饱和的磁曲率驱动的瑞利-泰勒(RT)不稳定性。耦合的非线性方程组的模型组演化的标量电场电位$ϕ$,等离子体密度$n$和磁矢量位$ψ$的平行分量。模拟已经在两个极限中进行,(i)低电阻率情况,其中RT是唯一的线性增长模式,以及(ii)高电阻率情况,其中漂移波是不稳定的,并且对于该高电阻率情况,磁曲率参数被设置为零以确保不存在RT增长。我们的模拟表明,在这两个限制的非线性稳定。的稳定机制是类似于早期的二维模拟中观察到的,即产生的带状剪切流的径向扩展的不稳定模式去相关。然而,在3d情况下的饱和非线性状态的性质不同于2d在一些重要的方面,如在短尺度上具有显着的功率水平和电磁波动的存在。虽然,在线性制度的电磁效应降低的增长率,在非线性制度中,它们的存在阻碍了稳定的过程中,通过抑制纬向流形成的过程。因此,非线性稳定发生的参数制度是相当大的减少,在三个维度。

英文摘要:

We present three dimensional fluid simulation results on the temporal evolution and nonlinear saturation of the magnetic curvature driven Rayleigh-Taylor (RT) instability. The model set of coupled nonlinear equations evolve the scalar electric field potential $ϕ$, plasma density $n$ and the parallel component of the magnetic vector potential $ψ$. The simulations have been carried out in two limits, (i) a low resistivity case in which RT is the only linearly growing mode, and (ii) a high resistivity case where the drift wave is unstable and for which the magnetic curvature parameter is set to zero to ensure the absence of the RT growth. Our simulations show nonlinear stabilization in both these limits. The stabilization mechanism is similar to that observed in earlier two dimensional simulations, namely the generation of zonal shear flows which decorrelate the radially extended unstable modes. However the nature of the saturated nonlinear state in the 3d case differs from that of 2d in some important ways such as by having significant levels of power in short scales and by the presence of electromagnetic fluctuations. Though, in the linear regime the electromagnetic effects reduce the growth rates, in the nonlinear regime their presence hinders the process of stabilization by inhibiting the process of zonal flow formation. Thus the parameter regime for which nonlinear stabilization takes place is considerably reduced in three dimensions.

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