Kinetic Studies of the Relativistic Pinch: A Key to Particle Acceleration in Astrophysical Plasmas

来自耀变体喷流和脉冲星风星云的快速燃烧的伽马射线和其他辐射信号表明，相对论性宇宙等离子体中能量耗散和粒子加速的标准模型可能是不正确的，这些模型会引发冲击波和磁流体扩散。这个项目使用强大的新计算工具来研究一个有希望的替代方案：通过无碰撞相对论等离子体中的重连接和湍流直接耗散磁能。这项研究将在一个更现实的天体物理背景下探索相对论性粒子加速和相关的辐射，而不是用于获得令人鼓舞的初步结果的理想配置。这项工作将使人们对黑洞与其宇宙环境的相互作用有更深入的了解。PIC模拟的创新方法可以应用于空间物理和实验室等离子体中的广泛问题。本科生有一系列相关的研究经验，以及博士后研究员的支持、培训和指导。通过与菲斯克天文馆的合作，利用模拟中视觉上引人注目的图形和动画，对公众科学素养做出了贡献。从理想配置开始的模拟显示出强大的非热粒子能量分布和变异性特征。粒子分布与等离子体的初始磁化有关，即磁能密度与相对论等离子体焓的比值。令人惊讶的是，在不同组成（对或电子-离子等离子体）的系统中，以及从理想的重连电流片到三维驱动湍流的设置中，也会出现类似的相关性。垂直动力学研究将跟踪不稳定磁流体动力捏缩结构的非线性发展，从而导致湍流、重连、粒子加速和辐射。由该团队开发并于2014年公开的Zeltron辐射粒子池（PIC）代码经过了良好的测试，可以对“动力学光束”进行全面分析，并研究微观动力学过程与宏观特征（如二次通量绳、电流片和体流）之间的关系。在相对论条件下，最先进的计算工具允许动力学和辐射等离子体现象与宏观磁流体动力学不稳定性相关。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

Rapidly flaring gamma-rays and other radiative signals from blazar jets and pulsar wind nebulae indicate that standard models for energy dissipation and particle acceleration in relativistic cosmic plasmas, which invoke shock waves and hydromagnetic diffusion, are probably incorrect. This project uses powerful new computational tools to study a promising alternative: the direct dissipation of magnetic energy through reconnection and turbulence in collisionless relativistic plasmas. The study will explore relativistic particle acceleration and the associated radiation in a much more realistic astrophysical context than the idealized configurations used to obtain encouraging preliminary results. This work will yield insights into the interactions of black holes with their cosmic environments. The innovative approaches to PIC simulation can be applied to a broad range of problems in space physics and laboratory plasmas. There is a range of associated research experiences for undergraduates, as well as support, training and mentorship for a postdoctoral researcher. Contribution to public scientific literacy comes through collaboration with the Fiske Planetarium, using visually arresting graphics and animations from the simulations.Simulations which have started from idealized configurations have shown robust nonthermal particle energy distributions and variability characteristics. The particle distributions correlate with the initial magnetization of the plasma, which is the ratio of magnetic energy density to relativistic plasma enthalpy. Surprisingly, similar correlations develop in systems with different compositions (pairs or electron-ion plasma) and in setups ranging from idealized reconnecting current sheets to three-dimensional driven turbulence. A vertical kinetic study will follow unstable magneto-hydrodynamic pinch configurations through their nonlinear development to the resulting turbulence, reconnection, particle acceleration, and radiation. The well-tested Zeltron radiative Particle-in-Cell (PIC) code, developed by this team and publicly available since 2014, enables a thorough analysis of "kinetic beaming," and a study of the relationships between microscopic kinetic processes and macroscopic features such as secondary flux ropes, current sheets, and bulk flows. State-of-the-art computational tools allow kinetic and radiative plasma phenomena to be related to macroscopic magnetohydrodynamic instability, under relativistic conditions.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.