Extreme Astrophysical Fluids, Magnetism and Radiation

极端天体物理流体、磁力和辐射

• 批准号: RGPIN-2017-06519
• 负责人: Thompson, Christopher
• 金额: $ 1.53万
• 依托单位: University of Toronto
• 依托单位国家: 加拿大
• 项目类别: Discovery Grants Program - Individual
• 财政年份: 2020
• 资助国家: 加拿大
• 起止时间: 2020-01-01 至 2021-12-31
• 项目状态: 已结题
• 来源: https://www.nserc-crsng.gc.ca/ase-oro/Details-Detailles_eng.asp?id=711816
• 关键词: Extreme; Astrophysical; Fluids; Magnetism; Radiation

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.

该提案解决了与 i) 极端天体物理磁性相关的问题； ii) 流体与强辐射场的相互作用； iii) 行星形成过程中固气混合物的物理学。 在过去的几年里，PI 与博士后和学生在所有这些领域发表了论文。 1. 磁星。 我们最近开发了一个中子星地壳的二维数值模型，其中包含弹性、塑性、磁力和热效应。 该模型对磁星明亮宽带电磁发射的起源做出了明确的预测，磁星由 1015 G 磁场的衰变提供动力。 我们将使用新计算的 QED 速率开发详细的光谱模型，并进一步探索二维塑性热模型对爆发后出现的衰减耗散尾部的预测。 2. 伽马射线爆发。我们最近开发了伽玛暴瞬发（0.1-100s）阶段的第一个自洽模型，i）以强磁化流出开始，ii）使用动力学计算来重现关键的观测特征（窄谱峰、非热光谱尾部，以及从硬到软的演化）。 光谱特征的独特预测反映在一些最近的数据中，这些数据将被更详细地研究。 3. 含有强辐射场的磁化流出物。 我们将研究来自辐射压力主导的吸积盘的磁离心流，扩展我们之前对射流加速度的计算。 风扭矩将针对各种径向磁通量分布进行计算，并应用于为超吸积物体和超大质量黑洞提供能量的盘的整体演化。 4. 相对论流出的相干低频发射。 脉冲星射电发射模型通常认为发射的等离子体仅限于磁层内。 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. 致密星中磁场的起源。我们最近研究了演化恒星对流辐射边界处磁螺旋度的泵浦。 这一过程将扩展到吸积恒星，以解决回收脉冲星、灾难变星和年轻大质量恒星的磁化问题。 6.极端固气混合物。行星的组装必须涉及极端状态，其中固体主导质量密度，气体主导压力。我们 2014 年对激波行为的计算，包括对粒子破碎和熔化的详细说明，将应用于星子/行星盘相互作用。 汤普森和史蒂文森开发的两相原月盘模型将适应更一般的条件，重点关注相交换在促进流出方面的作用。 公开代码 ATHENA 中的粒子解算器将更新以包含碎片效应。