CAREER: Magnetogenesis Revisited: The First Self-consistent Plasma Dynamo

宇宙是磁化的。从星系和星系团到太阳系，包括太阳和我们自己的星球，磁场几乎随处可见。它们无处不在的存在并不是被动的；相反，磁场是可观测宇宙的动态和形状中的关键角色。这种现象在地球上可能会产生重大的社会影响，太阳耀斑的例子就是例证。太阳耀斑是太阳磁场活动的戏剧性表现，直接影响空间天气，并可能对国家电网造成灾难性影响。因此，理解宇宙磁场产生的机制是等离子体物理学中的一个重要挑战。这一景观为学生提供了研究和培训的肥沃领域。这个项目将导致新的分析理论方法和最先进的超级计算机模拟的发展。该项目将侧重于重新评估初始磁场的重要性，这些磁场是为任何发电机提供种子所需的。在通常的范式中，传统的假设是这些都是通过比尔曼电池产生的。这样的领域是系统大小和薄弱的。然而，在无碰撞等离子体中，最近的从头计算结果表明，一种完全不同的范例可能更合适；事实上，数值模拟表明，导致比尔曼场的组态成为电子韦伯不稳定性的牺牲品。随之而来的种子场与比尔曼起源的种子场有根本的不同：它们相当强大，生活在接近电子皮肤深度的尺度上。因此，这一结果指向了一个不同的场景：事实上，等离子体发电机问题可能与其说是关于幅度，不如说是关于尺度：电子标度场在其自身的非线性演化和背景湍流的共同作用下，是否会在等分水平上产生大标度场？评估这样的种子场是如何进化的，以及至关重要的是，以这种方式播种的等离子发电机是否真的存在，是这个项目的关键目标。

The universe is magnetized. From galaxies and galaxy clusters to the solar system, including the Sun and our own planet, magnetic fields are found nearly everywhere we look. Their ubiquitous presence is not passive; rather, magnetic fields are key players in the dynamics and shape of the observable universe. Such phenomena can have significant societal implications here on Earth, as illustrated by the case of solar flares. Solar flares are dramatic manifestations of magnetic activity in the Sun that impact directly space weather and may catastrophically affect the national electric power grid. Therefore understanding the mechanisms responsible for cosmic magnetic fields is an important challenge in plasma physics. This landscape provides a fertile area of research and training for students. This project will lead to the development of novel analytical theoretical methods and state-of-the-art supercomputer simulations. This project will focus on reassessing the importance of the initial magnetic fields that are required to seed any dynamo. In the usual paradigm, the conventional assumption is that these arise via the Biermann battery. Such fields are system-size and weak. In collisionless plasmas, however, recent ab initio results suggest that an altogether different paradigm may be more appropriate; indeed, numerical simulations show that the configuration that gives rise to the Biermann fields becomes prey to the electron Weibel instability. The seed fields that ensue are radically different from those of Biermann origin: they are fairly strong, and live at scales close to the electron skin-depth. This result thus points to a different scenario: the plasma dynamo problem may not, in fact, be as much about amplitude as it is about scale: can electron-scale fields, under the combined action of their own nonlinear evolution and background turbulence, give rise to a large scale field at equipartition levels? Assessing how such seed fields evolve and, critically, whether a plasma dynamo seeded in this fashion may indeed exist, is the key goal in this project.