发表机构
Departament de Física, Universitat d’Alacant; Institut de Ciències de I’Espai (ICE-CSIC); Institut d’Estudis Espacials de Catalunya (IEEC)（阿利坎特大学物理系; 空间科学研究所（CSIC）; 加泰罗尼亚空间研究学院）
机构由 AI 辅助整理，请以论文原文为准。AI 中文总结
本研究通过三维磁热模拟发现，小尺度主导的初始磁场可导致脉冲星磁轴自发漂移，改变偶极场和倾角，从而解释不同年龄下制动指数偏离3的观测现象。
AI 中文摘要
对数百颗脉冲星的制动指数测量，尽管存在观测上的注意事项，却显示出清晰的趋势：早期年龄时$n<3$，中年时$n>3$，而在更大特征年龄时，数值越来越大且波动不定。孤立中子星的壳层磁场通过欧姆耗散和跨尺度的非线性霍尔重排演化，并伴有来自手征磁效应和埋藏后重新浮现的早期贡献。初始条件通常假设为偶极主导，而更复杂、更现实的磁场（能量更均匀地分布在一个广泛的尺度范围内）在此背景下尚未被探索。我们评估了初始非平凡场的内部动力学如何改变偶极场强度和倾角，以及它们对制动指数$n$的联合贡献与对准效应一起，如何与观测值相比较。为此，我们进行了长期的三维磁热模拟，配置范围从偶极主导情形到纠缠的、小尺度主导的场。具有弱偶极分量的小尺度主导配置显示出丰富的动力学：偶极模式不断由小尺度供给，并可能根据初始谱而增长或衰减，驱动$n<3$或$n>3$，而倾角在短至${\cal O}$(千年)的时间尺度上变化。这些自发变化通常主导对准力矩，并能解释在特征年龄$\tau_c\gtrsim10^5$年时观测到的任意符号的大$n-3$值，这与偶极主导模型不同。然而，短期的磁层波动或超流驱动的力矩变化可能仍需要用来定量解释测量结果和结构化的计时残差。未来将这些模型与观测到的计时特性进行比较的工作，可以微调最有希望的初始配置。
英文摘要
Braking index measurements of hundreds of pulsars, despite observational caveats, show a clear trend: $n<3$ at early ages, $n>3$ at middle ages, and increasingly large, fluctuating values at larger characteristic ages. Crustal magnetic fields in isolated neutron stars evolve through Ohmic dissipation and non-linear Hall redistribution across scales, with additional early-time contributions from the chiral magnetic effect and post-burial re-emergence. Initial conditions are usually assumed dipole-dominated, whereas more complex and realistic fields, with energy spread more evenly over a broad range of scales, have not been explored in this context. We assess how the internal dynamics of initially non-trivial fields change the dipolar field strength and obliquity, and how their combined contribution to the braking index $n$, together with that of the alignment, compares with the observed values. To this end we perform long-term 3D magneto-thermal simulations, for configurations ranging from the dipole-dominated case to tangled, small-scale-dominated fields. Small-scale dominated configurations with weak dipolar components show rich dynamics: the dipolar mode is continuously fed by the small scales and may grow or decay depending on the initial spectrum, driving $n<3$ or $n>3$, while the obliquity varies on timescales as short as ${\cal O}$(kyr). These spontaneous changes often dominate the alignment torque and can account for the large values of $n-3$ of either sign observed at characteristic ages $τ_c\gtrsim10^5$ yr, unlike the dipole-dominated models. However, short-term magnetospheric fluctuations or superfluid-driven variations of the torque may still be needed to explain the measurements and the structured timing residuals quantitatively. Future work comparing these models with the observed timing properties could fine-tune the most promising initial configurations.
Comments21 pages, 12 figures. Submitted for publication
