Relativistic Nonthermal Particle Acceleration in Kinetic Turbulence and Magnetic Reconnection: Connecting Simulations and Theory

在脉冲星风星云、吸积盘日冕和相对论喷流等不同的天体物理系统中，高度磁化的等离子体与加速带电粒子到非常高的速度有关。最近的许多进展都是数值上的，但这些庞大而复杂的模拟需要与一个连贯的理论图景联系起来，这也需要更新那些早于许多从计算中获得的见解的理论。这正是这个项目将提供的，推进我们对各种物理条件下加速的理解，扩展到太空和离地球更近的太阳等离子体，从而帮助在等离子体物理学、天体物理学和日球层物理学之间建立智力桥梁。这项研究包括对研究生的培训、支持和指导，以及对本科生的各种研究机会。通过与科罗拉多大学菲斯克天文馆合作呈现的视觉上引人注目的图形将有助于公众对现代科学的理解。具有扩展幂律能量分布的相对论性带电粒子被推断存在于许多天体物理系统中，但对非热粒子加速（NTPA）的机制知之甚少。直到最近，第一性原理动力学粒子池（PIC）模拟才表明，高磁化等离子体中的重连接和湍流可以有效地引起相对论性NTPA。将累积的数值结果转化为连贯的理论图像的挑战，由于现代PIC模拟的规模和复杂性，以及理论模型早于模拟并且没有更新的事实而加剧。NTPA的许多理论与Fokker-Planck （FP）方程有关，但没有数值证实。本项目将PIC模拟与解析理论相结合，确定FP方程方法是否适用，测量扩散和平流系数，必要时将超越FP，并阐明重连与湍流之间的更深层次联系。本项目将推进对各种物理条件下无碰撞磁重联和湍流中的相对论性NTPA的理论认识，并对理解中子星和黑洞周围的相对论性等离子体环境有重要贡献。通过影响其他空间和太阳等离子体对NTPA的思考，这项工作将有助于将等离子体物理学、天体物理学和日球层物理学联系起来。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。

Highly magnetized plasmas are implicated in accelerating charged particles to very high speeds in astrophysical systems as diverse as pulsar wind nebulae, accretion disk coronae, and relativistic jets. Much recent progress has been numerical, but these large and complex simulations need to be connected to a coherent theoretical picture, which also requires updating theories which predate many of the insights gained from computation. This is exactly what this project will provide, advancing our understanding of acceleration under various physical conditions, extending to space and solar plasmas closer to home, and thus helping to build intellectual bridges between plasma physics, astrophysics, and heliospheric physics. The study includes training, support, and mentoring for a graduate student as well as varied research opportunities for undergraduates. Visually arresting graphics presented through collaboration with the University of Colorado Fiske Planetarium will contribute to the public understanding of modern science.Relativistic charged particles with extended power-law energy distributions are inferred to exist in many astrophysical systems, but the mechanisms for non-thermal particle acceleration (NTPA) are poorly understood. Only recently have first-principles kinetic particle-in-cell (PIC) simulations suggested that reconnection and turbulence in highly magnetized plasmas can efficiently cause relativistic NTPA. The challenge of translating the accumulated numerical results into a coherent theoretical picture is exacerbated by the size and complexity of modern PIC simulations, and the fact that theoretical models predate the simulations and have not been updated. Many theories of NTPA are tied to the Fokker-Planck (FP) equation, but without numerical confirmation. This project will combine PIC simulations with analytical theory, determine whether the FP equation approach is applicable and measure the diffusion and advection coefficients, going beyond FP if necessary, and elucidate the deeper connections between reconnection and turbulence. This project will advance theoretical understanding of relativistic NTPA in collisionless magnetic reconnection and turbulence under a variety of physical conditions, and contribute significantly to understanding the relativistic plasma environments around neutron stars and black holes. By influencing thinking about NTPA in other space and solar plasmas, this work will help to connect plasma physics, astrophysics, and heliospheric physics.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.