Nonaxisymmetric Magnetorotational Instability in Proto-Neutron Stars
Nonaxisymmetric Magnetorotational Instability in Proto-Neutron Stars
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DOI：
10.1086/500391
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发表时间：
2005-12
期刊：
影响因子：
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通讯作者：
Y. Masada;T. Sano;H. Takabe
中科院分区：
文献类型：
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作者：
Y. Masada;T. Sano;H. Takabe
研究了具有环向磁场的差动旋转原中子星的稳定性。利用局部线性分析方法导出了非轴对称磁流体动力学不稳定性的稳定性判据。与正常恒星相比，PNS的旋转速度具有更强的径向剪切。我们发现，非轴对称的磁旋转不稳定性（NMRI）与一个大的方位波数m是占主导地位的扭结模式（m = 1）在差分旋转PNS。NMRI的增长率为角速度Ω量级，比扭结型不稳定性快几个数量级。稳定性的标准是类似的轴对称磁旋转不稳定性与极向场，虽然轻子梯度的影响被认为是在我们的分析。如果不稳定模态的波矢平行于Brunt-Väisälä振荡的恢复力，则NMRI甚至可以在对流稳定层中增长。NMRI的非线性演化可以放大PNS中的磁场并驱动MHD湍流，这可能导致中微子光度的增强。
We investigate the stability of differentially rotating proto-neutron stars (PNSs) with a toroidal magnetic field. Stability criteria for nonaxisymmetric MHD instabilities are derived using a local linear analysis. PNSs are expected to have much stronger radial shear in the rotation velocity compared to normal stars. We find that nonaxisymmetric magnetorotational instability (NMRI) with a large azimuthal wavenumber m is dominant over the kink mode (m = 1) in differentially rotating PNSs. The growth rate of the NMRI is of order the angular velocity Ω, which is faster than that of the kink-type instability by several orders of magnitude. The stability criteria are analogous to those of the axisymmetric magnetorotational instability with a poloidal field, although the effects of leptonic gradients are considered in our analysis. The NMRI can grow even in convectively stable layers if the wavevectors of unstable modes are parallel to the restoring force by the Brunt-Väisälä oscillation. The nonlinear evolution of NMRI could amplify the magnetic fields and drive MHD turbulence in PNSs, which may lead to enhancement of the neutrino luminosity.