磁星磁热演化中的朗道量子化电子：自由电子抗磁性增强焦耳加热与磁星加热问题
Magnetar magnetothermal evolution with Landau-quantized electrons: enhanced Joule heating due to free electron diamagnetism and the magnetar heating problem
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中文总结 AI 辅助
本研究通过模拟验证朗道量子化增强的焦耳加热，发现其虽能加速弱场磁星的能量耗散，但不足以解决强场磁星的加热问题。
中文摘要 AI 辅助
磁星在系统上比其他中子星更明亮。先前的研究表明，支持如此高的光度需要超出标准欧姆耗散的热源——即“磁星加热问题”。我们先前使用周期性盒模拟证明，中子星中朗道量子化诱导磁化的德哈斯-范阿尔芬（dHvA）振荡能够反复产生经历快速欧姆耗散的大梯度场分量。利用为此开发的QMFM有限体积代码，我们对真实中子星星壳进行了轴对称2.5维电子磁流体动力学加热演化模拟，包括所有朗道量子化效应，以量化这种对场耗散和恒星加热的增强。我们表明，朗道量子化效应产生强的小尺度磁场结构，其耗散可以将场约束的赤道热点加热到无朗道量子化时的温度之上。增强加热在较弱的初始场$B\sim10^{14}$ G时最为显著，此时磁能耗散速度加快30%：在这种情况下，星壳冷却到足以使dHvA振荡达到大振幅。对于为最明亮磁星提供能量所需的较强场$\gtrsim B\sim5\times10^{14}$ G，增强效果适中，因为这些场的耗散将星壳加热到足以热抑制dHvA振荡。在加热显著增强的情况下，大部分热量用于增加中微子光度，而表面光子光度仅略有增加。对于我们模拟的简单星壳约束场，朗道量子化增强的焦耳加热因此不足以解释磁星加热问题。
英文摘要
Magnetars are systematically more luminous than other neutron stars. Previous studies suggest that supporting such high luminosities requires a heat source beyond standard Ohmic dissipation-- the ``magnetar heating problem''. We previously demonstrated using periodic box simulations that de Haas--van Alphen (dHvA) oscillations of the Landau quantization-induced magnetization in a neutron star could repeatedly generate large-gradient field components that undergo rapid Ohmic dissipation. Using the QMFM finite volume code developed for this purpose, we perform axisymmetric 2.5D electron magnetohydrodynamics plus thermal evolution simulations of a realistic neutron star crust, including all Landau quantization effects, to quantify this enhancement to field dissipation and heating of the star. We show that Landau quantization effects generate strong, small-scale magnetic field structures whose dissipation can heat the field-confined equatorial hot spot beyond its temperature in the absence of Landau quantization. Enhanced heating is greatest for weaker initial fields $B\sim10^{14}$ G, for which magnetic energy is dissipated 30% faster: in this case, the crust cools sufficiently for the dHvA oscillations to reach large amplitudes. For the stronger fields $\gtrsim B\sim5\times10^{14}$ G required to power the most luminous magnetars, the enhancement is modest, as dissipation of these fields heats the crust sufficiently to thermally suppress dHvA oscillations. In cases where heating is significantly enhanced, most of the heat goes into increasing the neutrino luminosity, and surface photon luminosity is only slightly increased. For the simple crust-confined fields that we simulated, Landau quantization-enhanced Joule heating is thus insufficient to explain the magnetar heating problem.
发表机构
- Columbia Astrophysics Laboratory, Columbia University（哥伦比亚大学天体物理实验室，哥伦比亚大学）
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