Extreme Astrophysical Fluids, Magnetism and Radiation

这项建议涉及以下问题：1)极端天体物理磁性；2)流体与强辐射场的相互作用；3)行星形成过程中的固体-气体混合物的物理学。在过去的几年里，PI在所有这些领域都与博士后和学生一起发表了论文。我们最近开发了一个中子星外壳的二维数值模型，它包含了弹性、塑性、磁场和热效应。这个模型对磁星明亮的宽带电磁发射的起源做出了明确的预测，该发射是由1015G磁场的衰减提供动力的。我们将使用新计算的QED率建立详细的光谱模型，并进一步探索2D塑料-热模型对爆发后看到的衰变耗散尾巴的预测。我们最近发展了第一个伽玛暴瞬发(0.1-100s)相的自洽模型，即i)从强磁化外流开始，ii)使用动力学计算来再现关键的观测特征(窄谱峰、非热谱尾部和硬到软的演化)。对光谱特征的不同预测反映在一些最近的数据中，这些数据将进行更详细的调查。*3.含有强辐射场的磁化外流。我们将研究辐射压力占主导地位的吸积盘中的磁心偏心流动，扩展了我们以前对喷流加速的计算。风力矩将在大范围的径向磁通量分布下计算，并应用于馈送超吸积物体和超大质量黑洞的圆盘的全球演化。*4.相对论流出的相干低频辐射。脉冲星射电发射的模型通常假定发射的等离子体被限制在磁层内。我们将开发涉及相对论膨胀磁化壳的替代过程，这可能与快速射电爆发现象有关。5.致密恒星中磁场的起源。我们最近研究了演化恒星中对流-辐射边界处的磁螺旋度泵浦。这一过程将扩展到吸积恒星，以解决回收的脉冲星、激变变星和年轻的大质量恒星的磁化问题。行星的组装必须涉及极端状态，在这些极端状态下，固体主导质量密度，气体主导压力。我们2014年对激波行为的计算，包括对粒子碎裂和融化的详细描述，将应用于小行星/行星盘相互作用。汤普森和史蒂文森开发的两相原月圆盘模型将适用于更一般的条件，重点是相交换在促进外流方面的作用。公开可用的代码雅典娜中的粒子解算器将进行更新，以包括碎片效果。

This proposal addresses problems related to i) extreme astrophysical magnetism; ii) the interaction of fluids with intense radiation fields; and iii) the physics of solid-gas mixtures during planet formation. The PI has published in all these areas with post-docs and students over the last few years.******1. Magnetars. We recently developed a 2-dimensional numerical model of a neutron star crust that incorporates elastic, plastic, magnetic and thermal effects. This model makes distinct predictions for the origin of the bright broad-band electromagnetic emission of magnetars, which is powered by the decay of 1015 G magnetic fields. We will develop detailed spectral models using newly calculated QED rates, and further explore the predictions of the 2D plastic-thermal model for the decaying dissipative tails seen following outbursts.******2. Gamma-ray bursts. We recently developed the first self-consistent model of the prompt (0.1-100s) phase of a GRB that i) starts with a strongly magnetized outflow and ii) uses kinetic calculations to reproduce key observational features (a narrow spectral peak, non-thermal spectra tail, and hard-to-soft evolution). Distinct predictions of spectral features are mirrored in some recent data, which will be investigated in more detail. ******3. Magnetized outflows containing intense radiation fields. We will investigate magnetocentrifugal flows from radiation-pressure dominated accretion disks, extending our previous calculations of jet acceleration. The wind torque will be calculated for a wide range of radial magnetic flux profiles, and applied to the global evolution of disks feeding hyper-accreting objects and supermassive black holes. ******4. Coherent low-frequency emission from relativistic outflows. Models of pulsar radio emission generally posit that the emitting plasma is confined to the magnetosphere. We will develop alternative processes involving relativistically expanded magnetized shells, which may be relevant to the fast radio burst phenomenon.******5. Origin of magnetic fields in compact stars. We recently investigated the pumping of magnetic helicity at convective-radiative boundaries in evolved stars. This process will be extended to accreting stars, to address the magnetization of recycled pulsars, cataclysmic variables, and young, massive stars.******6. Extreme solid-gas mixtures. The assembly of planets must involve extreme states in which solids dominate the mass density and gas the pressure. Our 2014 calculation of shock behavior, including a detailed account of particle fragmentation and melting, will be applied to planetesimal/planet disk interaction. The model of a two-phase proto-lunar disk developed by Thompson & Stevenson will be adapted to more general conditions, with a focus on the role of phase exchange in facilitating outflows. The particle solver in the publicly available code ATHENA will be updated to include fragmentation effects.