Magnetic field decay with Hall drift in neutron star crusts
Magnetic field decay with Hall drift in neutron star crusts
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DOI：
10.1111/j.1365-2966.2012.20509.x
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发表时间：
2012-01
影响因子：
4.8
通讯作者：
Y. Kojima;S. Kisaka
中科院分区：
文献类型：
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作者：
Y. Kojima;S. Kisaka
研究了霍尔漂移下的磁场衰减动力学。假设轴对称磁场位于具有均匀电导率和电子数密度的球形地壳中，计算了磁场的长期演化直至欧姆耗散。从能量和螺旋度的角度探讨了极向和环向分量之间的非线性耦合。在强磁化状态下，漂移的非线性振荡只有在两个分量均分时才明显。当环面分量占主导地位时，显著的能量转移到极向分量。然而，反之则不然。一旦环面场不那么占主导地位，由于较大的阻尼率，它很快就会解耦。在霍尔漂移时间尺度上，表面的极场与初始偶极子有高度的畸变，但在较长的耗散时间尺度上又恢复到初始偶极子，因为它是最小阻尼形式。
The dynamics of magnetic field decay with Hall drift is investigated. Assuming that axisymmetric magnetic fields are located in a spherical crust with uniform conductivity and electron number density, the long-term evolution is calculated up to Ohmic dissipation. The non-linear coupling between poloidal and toroidal components is explored in terms of their energies and helicity. Non-linear oscillation of the drift in strongly magnetized regimes is clear only around equipartition between the two components. Significant energy is transferred to the poloidal component initially when the toroidal component dominates. However, the reverse is not true. Once the toroidal field is less dominant, it quickly decouples due to a larger damping rate. The polar field at the surface is highly distorted from the initial dipole during the Hall drift time-scale, but returns to the initial dipole over a longer dissipation time-scale, since it is the least damped form.