Three-dimensional Dynamics of Strongly Twisted Magnetar Magnetospheres: Kinking Flux Tubes and Global Eruptions
Three-dimensional Dynamics of Strongly Twisted Magnetar Magnetospheres: Kinking Flux Tubes and Global Eruptions
复制标题
DOI：
10.3847/2041-8213/accada
复制
发表时间：
2023-02
期刊：
影响因子：
--
通讯作者：
J. Mahlmann;A. Philippov;V. Mewes;B. Ripperda;E. Most;L. S. D. O. A. Sciences;Peyton Hall;P. Universi
中科院分区：
文献类型：
--
作者：
J. Mahlmann;A. Philippov;V. Mewes;B. Ripperda;E. Most;L. S. D. O. A. Sciences;Peyton Hall;P. Universi
来自磁星（高度磁化的中子星）的各种硬x射线爆发的起源仍然未知。我们确定了相对论性磁球的不稳定性，这可以解释一系列x射线耀斑的亮度。地壳表面运动可以通过改变载流磁束中磁力线的冻结脚点来扭曲磁星磁层。轴对称（2D）磁球表现出强烈的喷发动力学，即由临界脚点位移ψ crit≥π触发的灾难性横向不稳定性。相比之下，我们新的具有有限表面扩展的三维（3D）扭曲模型捕获了偶极磁球中扭曲力无通量束的重要非轴对称动力学。除了由横向不稳定导致的公认的全球喷发（如二维），这种三维结构可以形成螺旋状、扭结状的动力学，并在局部耗散能量（受限喷发）。在强大的全球爆发中，高达25%的诱导扭转能量被耗散，并可用于为x射线耀斑提供动力，我们的大多数模型显示能量释放在最常见的x射线爆发范围内，小于1043 erg。当大量能量在深埋于偶极磁层时，就会发生这样的事件。由于间歇性的不稳定性和持续扭曲的通量管的受限喷发，能量较低的爆发可能先于强大的耀斑。一旦达到临界状态，全球爆发就会产生必要的坡因廷通量主导的流出物，这是描述磁星风中快速射电暴产生的模型所要求的，例如，通过相对论性磁重联或冲击。
The origins of the various outbursts of hard X-rays from magnetars (highly magnetized neutron stars) are still unknown. We identify instabilities in relativistic magnetospheres that can explain a range of X-ray flare luminosities. Crustal surface motions can twist the magnetar magnetosphere by shifting the frozen-in footpoints of magnetic field lines in current-carrying flux bundles. Axisymmetric (2D) magnetospheres exhibit strong eruptive dynamics, i.e., catastrophic lateral instabilities triggered by a critical footpoint displacement of ψ crit ≳ π. In contrast, our new three-dimensional (3D) twist models with finite surface extension capture important non-axisymmetric dynamics of twisted force-free flux bundles in dipolar magnetospheres. Besides the well-established global eruption resulting (as in 2D) from lateral instabilities, such 3D structures can develop helical, kink-like dynamics, and dissipate energy locally (confined eruptions). Up to 25% of the induced twist energy is dissipated and available to power X-ray flares in powerful global eruptions, with most of our models showing an energy release in the range of the most common X-ray outbursts, ≲1043 erg. Such events occur when significant energy builds up while deeply buried in the dipole magnetosphere. Less energetic outbursts likely precede powerful flares, due to intermittent instabilities and confined eruptions of a continuously twisting flux tube. Upon reaching a critical state, global eruptions produce the necessary Poynting-flux-dominated outflows required by models prescribing the fast radio burst production in the magnetar wind—for example, via relativistic magnetic reconnection or shocks.