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。最极端的太空天气事件涉及来自太阳的大规模喷发，称为“日冕物质抛射”，或称日冕物质抛射，可以以每小时数百万英里的速度向地球移动。当它们到达地球磁场--“磁层”的影响时，这些日冕物质抛射会引发令人惊叹的极光显示，但也会对卫星、通信和电网造成不利影响。然而，耦合的太阳-地球系统是一个复杂的动态环境，具有相互关联的物理过程，范围从不到一秒到几天，从几米到数百万英里。因此，了解和预测磁层的反应，以及形成危险“辐射带”的被困高能粒子群，对空间物理学和空间气象界来说是一项巨大的挑战，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，这一挑战具有日益重要的意义。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天气事件进行建模。它建立在三个截然不同的最新进展的基础上；日光层磁流体动力学模型，它可以捕捉起源于太阳的复杂上游现象；蛇发六磁流体模型，它可以捕捉大规模的太阳-风-磁层相互作用；以及高能粒子模型，它被整合在蛇发星座上。粒子模型成功地扩展到数千个CPU，因此可以模拟具有特征的亚秒时间尺度的粒子集合，跨越多天的极端空间天气事件。为了理解背后的物理原理，我将重点介绍在太空时代观察到的一系列极端事件，以及即将发生的第25太阳周期(2019-2030年)的事件，在这些事件中，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。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太阳风条件可以迅速产生和摧毁整个辐射带。在此之后，我将开发平流粒子模型，以包括扩散输送并调整它，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-平流理论来改进辐射带预报。最后，我将自洽地将来自粒子的反馈合并到修正的MHD方程中，并研究来自非热粒子的反馈是产生一个根本不同的磁层系统，还是产生一个周期性发散的磁层系统。这对行星磁层和太阳外行星磁层产生了深远的影响，在这些地方，由人口众多的M星产生的日冕物质抛射在确定宜居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.