Extreme Astrophysical Fluids, Magnetism and Radiation

这一建议解决了以下问题：1)极端天体物理磁性；Ii)流体与强辐射场的相互作用；iii)行星形成过程中固体-气体混合物的物理学。在过去的几年里，PI与博士后和学生一起在所有这些领域发表了文章。******1。磁星。我们最近开发了一个包含弹性、塑性、磁性和热效应的中子星外壳的二维数值模型。这个模型对磁星明亮的宽带电磁发射的起源做出了独特的预测，这种电磁发射是由1015g磁场的衰变提供动力的。我们将使用新计算的QED速率开发详细的光谱模型，并进一步探索爆发后衰减耗散尾的二维塑性热模型的预测。******2。伽马射线爆发。我们最近开发了第一个自一致的GRB瞬发期（0.1-100秒）模型，该模型i)从强磁化流出开始，ii)使用动力学计算来重现关键的观测特征（窄光谱峰，非热光谱尾和硬到软的演化）。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。风转矩将在大范围的径向磁通量剖面上计算，并应用于提供超吸积物体和超大质量黑洞的圆盘的全局演化。* * * * * * 4。相对论性流出的相干低频发射。脉冲星射电发射模型通常假定发射等离子体局限于磁层。我们将发展涉及相对论膨胀磁化壳的替代过程，这可能与快速射电暴现象有关。******5。致密恒星磁场的起源。我们最近研究了演化恒星在对流-辐射边界处的磁螺旋度泵送。这个过程将扩展到吸积恒星，以解决循环脉冲星，灾难性变量和年轻的大质量恒星的磁化问题。******6。极端的固体-气体混合物。行星的聚集必然涉及极端状态，在这种状态下，固体的质量密度占主导地位，气体的压力占主导地位。我们2014年对冲击行为的计算，包括粒子破碎和熔化的详细描述，将应用于星子/行星盘的相互作用。汤普森和史蒂文森开发的两相原月球盘模型将适用于更一般的条件，重点关注相交换在促进流出中的作用。公开代码ATHENA中的粒子求解器将被更新以包含碎片效果。

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.