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

宇宙被磁化了。从星系和星系团到太阳系，包括太阳和我们自己的星球，磁场几乎无处不在。它们无处不在的存在不是被动的;相反，磁场是可观测宇宙的动力学和形状的关键角色。这种现象在地球上可能产生重大的社会影响，太阳耀斑的情况就说明了这一点。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，理解宇宙磁场的机制是等离子体物理学的一个重要挑战。这一景观为学生提供了研究和培训的肥沃区域。该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。 这个项目将集中于重新评估初始磁场的重要性，这些磁场是任何发电机的种子。在通常的范例中，传统的假设是这些通过比尔曼电池产生。这些领域是系统规模和薄弱。然而，在无碰撞等离子体中，最近的从头计算结果表明，一个完全不同的范式可能更合适;事实上，数值模拟表明，产生比尔曼场的配置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完全不同：它们相当强大，并且生活在接近电子趋肤深度的尺度上。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振幅无关，而与尺度有关：电子尺度的场，在其自身的非线性演化和背景湍流的共同作用下，能在均分水平上产生大尺度场吗？评估这种种子场是如何演变的，以及关键的是，以这种方式播种的等离子发电机是否确实存在，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.