Collaborative Research: Three-Dimensional Stability of Kinetic Flux Rope Structures in a Collisionless Magnetized Plasma

本项目将从理论上和计算上研究等离子体中自组织结构的形成。宇宙中大多数可观察到的物质都是以等离子体的形式存在的，等离子体由带电粒子和从原子中释放出来的电子组成。在等离子体中，电子和带电原子（离子）的运动是准随机的，但它们的空间分布和运动可以产生电场和磁场，导致等离子体结构的形成，其尺寸远远大于原子尺寸，但远远小于整个等离子体的体积。这样的小结构可以从根本上改变等离子体的特性。然而，是否以及如何形成这样的结构仍然知之甚少，这将在本项目中进行。这项研究的结果将增加我们对空间、天体物理学和实验室等离子体特性的理解，对空间天气预报和未来的聚变能装置具有重要的社会应用。这个合作项目将支持阿拉斯加费尔班克斯大学的一名博士生，以及新罕布什尔大学的一名博士生。学生们将接受理论和数值模拟方面的培训。高温等离子体可以被认为是无碰撞的，无碰撞等离子体中的粒子分布通常偏离麦克斯韦方程。虽然这种非麦克斯韦分布的形式很重要，但探索如何在这样的等离子体中存在小尺度动力学结构也很重要，一维中的伯恩斯坦-格林-克鲁斯卡尔（BGK）模式就是一个例子。该项目将使用最先进的粒子单元（PIC）代码“PSC”进行数值模拟，以研究满足vlasov - poisson - ampantore方程组的磁通量绳形式的局部动力学结构的解析多维解的稳定性。生成稳定的二维或三维局部动力学结构的可能形成机制也将在数值上进行研究。本研究的主要目的是定量表征动力学结构稳定的条件。该项目有望对无碰撞磁化等离子体的小尺度动力学物理学产生新的认识。通过该项目获得的新见解将对基础等离子体理论产生影响，并影响实验室，空间和天体物理等离子体的前沿问题。例如，它可以对理解磁重联过程具有重要意义，其中最近的大规模动力学模拟发现了磁重联过程中产生的小动力学尺度通量绳。以研究空间磁重联为主要目标的磁层多尺度（MMS）任务也观测到了小尺度动力学结构。此外，由于弗拉索夫方程广泛应用于许多不同的物理系统，该项目可以影响科学的其他领域。该项目由物理系和促进竞争性研究的既定计划（EPSCoR）共同资助。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。

This project will theoretically and computationally study formation of self-organized structures in a plasma. Most observable matter in the universe is in the form of a plasma, consisting of electrically charged particles with electrons freed from atoms. In a plasma, the electrons and the charged atoms (the ions) move quasi-randomly, but their spatial distribution and movement can produce electric and magnetic fields leading to formation of plasma structures with sizes much larger than atomic sizes but much smaller than the volume of the whole plasma. Such small structures can fundamentally change the properties of plasmas. However, whether and how such structures can form is still poorly understood and will be pursued within this project. Results from this research will increase our understandings of properties of space, astrophysical, and laboratory plasmas, with societally important applications for space weather prediction and future fusion energy devices. This collaborative project will support a PhD student at University of Alaska Fairbanks, as well as a PhD student at University of New Hampshire. The students will receive training in both theory and numerical simulations.High temperature plasmas can be considered collisionless, with particle distributions in a collisionless plasma often deviating from a Maxwellian. While the forms of such non-Maxwellian distributions are important, it is also important to explore how small-scale kinetic structures can exist in such plasmas, with the Bernstein-Greene-Kruskal (BGK) modes in 1D being one example. This project will perform numerical simulations using the state-of-the-art Particle-In-Cell (PIC) code "PSC" to study the stability of analytic multi-dimensional solutions of localized kinetic structures in the form of magnetic flux ropes satisfying the Vlasov-Poisson-Ampère system of equations. Possible formation mechanisms for the generation of stable two-dimensional or three-dimensional localized kinetic structures will also be studied numerically. The main goal of this research is to characterize quantitatively the conditions under which kinetic structures can be stable. This project is expected to produce new understanding of small-scale kinetic physics in collisionless magnetized plasmas. New insights obtained through this project will have impact on fundamental plasma theory, as well as affect frontier problems in laboratory, space and astrophysical plasmas. For example, it can have significant implication for understanding the process of magnetic reconnection, where recent large-scale kinetic simulations have discovered the generation of small kinetic scale flux ropes during magnetic reconnection. Small-scale kinetic structures have also been observed by the Magnetospheric Multiscale (MMS) mission, which has the main objective of studying magnetic reconnection in space. Moreover, this project can impact other fields in science since the Vlasov equation is widely applied in many different physical systems. This project is jointly funded by the Division of Physics and the Established Program to Stimulate Competitive Research (EPSCoR).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.