Solar and Magnetospheric Plasmas: Theory and Application

圣安德鲁斯大学的太阳和磁层理论小组(SMTG)将致力于研究太阳大气层和地球磁层中发生的基本物理过程，以解决STFC路线图的关键问题：太阳如何影响地球和太阳系其他部分的环境？特别是，这项拟议的工作解决了一些问题，例如：i)太阳表面下方出现的磁场在与太阳大气相互作用时如何释放能量？ii)为什么太阳外层大气(日冕)的温度比其可见表面高100倍以上？三)太阳表面的多尺度过程如何影响太阳全球磁场的演变以及它何时变得不稳定？四)我们能否使用基于物理的模拟技术来预测太阳喷发及其对地球的影响？五)地球磁层中观测到的波是由什么引起的，如何利用模型来改进我们对磁层观测的解释？要找到这些关键问题的答案，需要一系列的专业知识。SMTG非常适合回答这些问题，因为我们使用基础理论、分析模型、计算机模拟、正演模拟和观测相结合的方法来研究各种物理现象。这种详细的建模和与几次卫星飞行任务的观测结果的比较对于取得进展是至关重要的。我们将利用等离子体理论研究的主题是：i)磁通量出现、重联和粒子加速的复杂相互作用，ii)使太阳大气比太阳表面热得多的物理机制(大气加热)，iii)全球日冕磁场的结构和稳定性的演变，iv)基于物理和数据驱动的预测太阳爆发的方法的发展，v)3D非均匀介质中MHD波的耦合。这些现象遵守可以表示为一组非线性偏微分方程组的物理规律。然而，它们的不同之处在于，不同的现象需要不同的主导术语。因此，物理过程和等离子体响应在每种情况下都将是不同的。例如，磁重联需要电阻，但MHD波一般不需要。重力在磁通浮现和日冕形成中很重要，但对于磁重联却不重要。太阳耀斑中的粒子加速可能需要粒子描述，而其他许多研究领域不需要。正是非线性方程的高度复杂性使得它们很难求解，也很难确定哪些关键物理过程对每个事件负责。为了求解这些复杂的方程，我们需要一个非常重要的研究工具，即高性能计算。一个研究问题可以被分成几个较小的部分，这些部分同时在不同的处理器上运行(并行)。因此，使用多个处理器，在单个处理器上需要多年的工作将在几周内完成。我们在STFC科学路线图中解决了关键问题。然而，详细了解我们研究课题的物理学不仅对太阳、类太阳恒星和空间天气很重要，而且对于理解一系列不同的天体物理过程也很重要，例如巨型分子云中恒星的形成，恒星、黑洞和活动星系核周围天体物理盘的演化，以及从恒星到星系外尺度的风和流出的物理。

The Solar and Magnetospheric Theory Group (SMTG) of the University of St Andrews will work on the fundamental physical processes occurring in the Sun's atmosphere and the terrestrial magnetosphere to address the key STFC Roadmap question "How does the Sun influence the environment of the Earth and the rest of the Solar System?" In particular, the proposed work addresses questions, such as:i) How do magnetic fields emerging from below the solar surface release energy when interacting with the solar atmosphere?ii) Why is the Sun's outer atmosphere (the corona) over 100 times hotter than its visible surface? iii) How do multiscale processes in the solar surface affect the evolution of the Sun's global magnetic field and when it becomes unstable? iv) Can we use physics-based modelling techniques to predict solar eruptions and their effect on Earth?v) What causes the observed waves in the Earth's magnetosphere and how can models be used to improve our interpretation of magnetospheric observations ? Finding answers to these key questions calls for a range of expertise. The SMTG is excellently positioned to answer these questions, since we study a wide variety of physical phenomena using a combination of fundamental theory, analytical models, computer simulations, forward modelling and observations. This mixture of detailed modelling and comparison with observations from several satellite missions is essential to make progress. The topics we will investigate, using plasma theory, are: i) the complex interplay of magnetic flux emergence, reconnection and particle acceleration,ii) the physical mechanisms responsible for keeping the solar atmosphere much hotter than the solar surface (atmospheric heating), iii) the evolution of the structure and stability of the global coronal magnetic field, iv) the development of physics-based and data-driven methods to predict solar eruptions,v) the coupling of MHD waves in 3D nonuniform media.These phenomena obey physical laws that can be expressed as a set of non-linear partial differential equations. However, what makes them distinct is that different phenomena require different dominant terms. Hence, the physical processes and the plasma response will be different in each case. For example, magnetic reconnection requires electrical resistance, but MHD waves in general do not. Gravity is important in flux emergence and prominence formation, but for magnetic reconnection it is not. Particle acceleration in solar flares may require a particle description, while many of the others research areas do not. It is the rich complexity of the non-linear equations that makes them hard to solve and to determine which key physical processes are responsible for each event. In order to solve these complex equations, we need a very important research tool, namely High Performance Computing. A research problem can be split up into smaller parts that are run on different processors at the same time (in parallel). Hence, with multiple processors a job that would require many years on a single processor, will be completed in a few weeks.We address key issues in the STFC Science Roadmap. However, a detailed understanding of the physics of our research topics are important not only for the Sun, solar-like stars and space weather, but also for understanding a range of diverse astrophysical processes such as star formation in giant molecular clouds, the evolution of astrophysical discs around stars, black holes and in Active Galactic Nuclei, and the physics of winds and outflows from stellar to extragalactic scales.