Modelling Extreme Space Weather Events

空间天气描述了太阳上的活动如何影响我们在太空中的卫星和地球上的生命。最极端的空间天气事件涉及太阳的大规模爆发，称为“日冕物质抛射”或CME，它可以以每小时数百万英里的速度向地球传播。当它们到达地球磁场的影响时，这些CME会引发惊人的极光显示，但会对卫星，通信和电网产生不利影响。然而，日地耦合系统是一个复杂的动态环境，其相互关联的物理过程跨越从不到一秒到几天，从几米到几百万英里的尺度。因此，了解和预测磁层的反应以及形成危险的“辐射带”的被困高能粒子群是对空间物理学和空间气象界的一项巨大挑战，但随着我们进入卫星巨型星座时代和人类计划在月球上建立存在，这一挑战也越来越重要。该研究金将侧重于利用机构和国家高性能计算设施对极端空间气象事件进行建模。它是建立在三个不同的最新进展：日光层磁流体动力学（MHD）模型，可以捕捉复杂的上游现象起源于太阳; Gorgon MHD模型，可以捕捉大规模的太阳风磁层相互作用;和高能粒子模型，这是集成在Gorgon。粒子模型成功地扩展到数千个CPU，因此可以模拟具有特征亚秒时间尺度的粒子集合，跨越多日极端空间天气事件。为了理解潜在的物理学，我将重点关注太空时代观察到的一系列极端事件，以及太阳活动周期25期间即将发生的事件（2019-2030），欧空局的太阳轨道器和美国宇航局的帕克太阳探测器航天器能够从更接近太阳的地方提供前所未有的洞察力。我将利用这套模拟模型来实现三个不同的目标：我将首先全面研究什么样的太阳风条件可以迅速创造和摧毁整个辐射带。在此之后，我将开发平流粒子模型，以纳入扩散传输，并调整它以匹配最先进的福克普朗克辐射带模型（RBM）。然后，我将直接识别和约束平流输送过程，并确定适当的扩散平流理论，以改善辐射带预报。最后，我将自洽地将粒子反馈纳入修正的MHD方程，并研究来自非热粒子的反馈是否会产生一个根本不同的磁层系统或周期性发散的系统。这对行星磁层和太阳系外行星磁层有着深远的影响，其中来自人口众多的M星的CME在定义可居住性方面发挥着重要作用。

Space weather describes how activity on the Sun impacts our satellites in space and life here on Earth. The most extreme space weather events involve vast eruptions from the Sun, called "coronal mass ejections", or CMEs, which can travel towards Earth at millions of miles an hour. When they reach the influence of the Earth's magnetic field, the "magnetosphere", these CMEs trigger amazing auroral displays but can adversely affect satellites, communications and power grids. The coupled Sun-Earth system is, however, a complex dynamical environment with inter-related physical processes extending across scales ranging from less than a second to days, and from metres to millions of miles. Understanding and predicting the response of the magnetosphere, and trapped populations of energetic particles which form the hazardous "radiation belts", thus represents an immense challenge to the space physics and space weather communities, but one of increasing relevance as we move into the era of satellite mega-constellations and with humanity planning to establish a presence on the moon. This fellowship will focus on the modelling of extreme space weather events, using institutional and national high-performance-computing facilities. It is built upon three distinct recent advances; a heliospheric magnetohydrodynamic (MHD) model which can capture complex upstream phenomena originating at the Sun; the Gorgon MHD model which can capture the large-scale solar-wind-magnetosphere interaction; and an energetic Particle model which is integrated in Gorgon. The Particle model successfully scales to thousands of CPUs and can thus simulate ensembles of particles with characteristic sub-second timescales, across multi-day extreme space weather events. In order to understand the underlying physics, I will focus on a series of extreme events observed in the Space Age, as well as upcoming events during Solar Cycle 25 (2019-2030) where ESA's Solar Orbiter and NASA's Parker Solar Probe spacecraft are able to provide unprecedented insight from closer to the Sun.I will utilise this suite of simulation models to achieve three distinct goals: I will firstly comprehensively examine what solar wind conditions can rapidly create and destroy entire radiation belts. Following this, I will develop the advective Particle model to incorporate diffusive transport and tune this to match state-of-the art Fokker Planck Radiation Belt Models (RBMs). I will then directly identify and constrain advective transport processes, and determine appropriate diffusive-advective theories for improved radiation belt forecasting. Finally, I will self-consistently incorporate feedback from the particles into modified MHD equations, and study whether feedback from non-thermal particles produces a fundamentally different magnetospheric system or one that periodically diverges. This has far-reaching consequences for planetary magnetospheres and also extra-solar planetary magnetospheres where CMEs deriving from populous M stars play a significant role in defining habitability.