论文标题
在中子星形地壳中带有分数磁性螺旋的霍尔级联
Hall cascade with fractional magnetic helicity in neutron star crusts
论文作者
论文摘要
人们普遍认为，中子恒星壳中磁场的欧姆衰变受Hall Drift的控制，这导致了所谓的Hall Cascade。在这里，我们表明，螺旋和分数的螺旋磁场会像磁水动力学（MHD）一样经历强大的逆级联，但是随着时间的时间$ t $：$ \ propto t^{ - 2/5} $而不是$ \ propto t^{ - propto t^{ - 2/3} $。即使对于非螺旋磁场，对于足够强的磁场也有一定程度的逆级联。与WaveNumber $ K $的惯性范围与强制大厅级联的早期发现兼容，即与$ k^{ - 7/3} $成比例，但是在衰减的情况下，近代范围的光谱频谱陡峭到新颖的$ k^5 $ slope，而不是$ k^4 $ slope in mhd in mhd in mhd in mhd。大规模磁场的能量可以通过反级联反向及时增加四倍。对于螺旋场，发现能量耗散与大规模磁场成反比，并且与根平方（RMS）磁场的第五功率成反比。对于具有几次RMS磁场$ 10^{14} \，$ g的中子星条件，大规模磁场可能仅为$ 10^{11} \，$ g，而仍产生$ 10^{33} \，$ s $ s $ s $ s $^{ - 1} $的磁耗散的磁耗散，可以为千年的$ sistort of surestirestion surestirestion tosist tosist torestion nosist。最后，这表明，局部未分层模型的结论与具有边界的分层模型的结论非常吻合。
The ohmic decay of magnetic fields in the crusts of neutron stars is generally believed to be governed by Hall drift which leads to what is known as a Hall cascade. Here we show that helical and fractionally helical magnetic fields undergo strong inverse cascading like in magnetohydrodynamics (MHD), but the magnetic energy decays more slowly with time $t$: $\propto t^{-2/5}$ instead of $\propto t^{-2/3}$ in MHD. Even for a nonhelical magnetic field there is a certain degree of inverse cascading for sufficiently strong magnetic fields. The inertial range scaling with wavenumber $k$ is compatible with earlier findings for the forced Hall cascade, i.e., proportional to $k^{-7/3}$, but in the decaying cases, the subinertial range spectrum steepens to a novel $k^5$ slope instead of the $k^4$ slope in MHD. The energy of the large-scale magnetic field can increase quadratically in time through inverse cascading. For helical fields, the energy dissipation is found to be inversely proportional to the large-scale magnetic field and proportional to the fifth power of the root-mean square (rms) magnetic field. For neutron star conditions with an rms magnetic field of a few times $10^{14}\,$G, the large-scale magnetic field might only be $10^{11}\,$G, while still producing magnetic dissipation of $10^{33}\,$erg$\,$s$^{-1}$ for thousands of years, which could manifest itself through X-ray emission. Finally, it is shown that the conclusions from local unstratified models agree rather well with those from stratified models with boundaries.
