Solar and Magnetospheric Magnetohydrodynamics and Plasmas: Theory and Application

圣安德鲁斯大学的太阳和磁层理论小组（SMTG）将研究太阳大气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余部分的环境？”特别是，提出的工作解决的问题，如：i)太阳黑子和活跃区域（强磁场区域）如何形成，演变和衰变？为什么太阳的外层大气（日冕）比其可见表面要热100多倍？iii)太阳大气和地球磁层中观测到的波的原因是什么？iv)多年来太阳的磁场是如何演变的，它是如何与地球相互作用的？v)三维磁场如何改变其连通性/结构，我们将观察到什么特性？vi)带电粒子在重联过程中是如何加速的？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，正演建模和观测相结合来研究各种各样的物理现象。这种详细建模和与几个卫星任务的观测结果进行比较的混合对取得进展至关重要。我们将使用等离子体理论研究的主题是：i)太阳黑子和活动区域的形成和演化，ii)保持太阳大气比太阳表面热得多（大气加热）的物理机制，iii)磁流体动力学（MHD）波的能量平衡，iv)由于磁场重联和能量释放以及粒子加速到高能而引起的观测特征，v)全球日冕磁场的演化和拓扑结构，vi)三维非均匀介质中MHD波的耦合。这些现象所遵循的物理定律可以用一组非线性偏微分方程来表示。然而，使它们不同的是，不同的现象需要不同的主导术语。因此，在每种情况下，物理过程和等离子体响应将是不同的。例如，磁重联需要电阻，但MHD波一般不需要。重力在通量的产生和日珥的形成中是重要的，但在磁重联中则不是。太阳耀斑和磁层中的粒子加速可能需要动力学（粒子）描述，而许多其他研究领域则不需要。正是非线性方程的丰富复杂性使得它们很难求解，也很难确定每个事件的关键物理过程。为了解决这些复杂的方程，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解成更小的部分，同时在不同的处理器上运行（并行）。因此，如果使用256个处理器，在单个处理器上需要10年才能完成的工作将在几周内完成。我们讨论了STFC科学路线图中的关键问题。然而，详细了解我们的研究主题的物理学不仅对太阳，类太阳恒星和空间天气很重要，而且对理解一系列不同的天体物理过程也很重要，例如巨大分子云中的恒星形成，恒星周围天体物理盘的演化，黑洞和活动星系核，以及从恒星到星系外尺度的风和流出物的物理学。

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 sunspots and active regions (regions of strong magnetic fields) form, evolve and decay? ii) Why is the Sun's outer atmosphere (the corona) over 100 times hotter than its visible surface? iii) What causes the observed waves in the Sun's atmosphere and the Earth's magnetosphere? iv) How does the Sun's magnetic field evolve over many years and how does it interact with the Earth? v) How does a 3D magnetic field change its connectivity/configuration and what properties would we observe? vi) How are charged particles accelerated during reconnection? 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 formation and evolution of Sunspots and Active Regions, ii) the physical mechanisms responsible for keeping the solar atmosphere much hotter than the solar surface (atmospheric heating), iii) the energy budget of magnetohydrodynamics (MHD) waves, iv) observational signatures due to magnetic field reconnection and energy release and the acceleration of particles to high energies, v) the evolution and topology of the global coronal magnetic field, vi) 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 and the magnetosphere may require a kinetic (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 256 processors a job that would require 10 years on 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.