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)将致力于太阳大气层和行星磁层中发生的基本物理过程，这些过程有助于解决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？”例如，拟议的工作涉及如下问题：i)太阳黑子和活动区(强磁场区域)是如何形成、演化和衰变的？Ii)为什么太阳的外层大气(日冕)比它的可见表面热100倍以上？三)太阳大气层和地球磁层中观测到的波的原因是什么？IV)太阳的磁场是如何在多年中演变的，它是如何与地球相互作用的？V)3D磁场如何改变其构型？6)带电粒子在太阳耀斑和喷发期间是如何加速的？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，因为我们使用数学模型(基本理论、分析模型、计算机模拟、正演模型和观测的组合)研究各种物理现象。这正是所需要的，即混合使用详细的建模方法，并将几次卫星飞行任务的观测结果与理论模型进行比较。我们将使用等离子体理论研究的主题是：i)太阳内部磁场的出现及其随后的演化，冷密度日冕的形成和太阳全球磁场的演化，ii)磁流体(MHD)波的传播和耗散，iii)磁场改变其连通性、释放过剩能量和粒子如何加速到高能的3D物理机制，iv)使太阳大气保持比太阳表面热得多的物理机制(大气加热)，v)全球日冕磁场的演化和拓扑，六)三种不同磁层磁流体波的耦合以及行星磁层与其电离层的耦合物理。这些现象遵循可以用非线性偏微分方程组表示的物理定律。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。太阳耀斑和磁层中的粒子加速需要动力学(粒子)描述，而许多其他研究领域不需要。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。一个非常重要的研究工具是高性能计算。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，拥有256个处理器，在单个处理器上需要10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，而且对于理解这些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 planetary magnetospheres that help to address the key STFC Roadmap question "How does the Sun influence the environment of the Earth and the rest of the Solar System?" For example, 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 configuration? vi) How are charged particles accelerated during solar flares and eruptions? 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 mathematical modelling (a combination of fundamental theory, analytical models, computer simulations, forward modelling and observations). This is exactly what is needed, i.e. a mixture of detailed modelling methods and a comparison between observations from several satellite missions and the theoretical models. The topics we will investigate, using plasma theory, are: i) the emergence of magnetic fields from the solar interior and their subsequent evolution, the formation of cool dense prominences and the evolution of the global magnetic field of the Sun, ii) the propagation and dissipation of magnetohydrodynamics (MHD) waves, iii) the physical 3D mechanisms by which magnetic fields change their connectivity, releasing excess energy and how particles are accelerated to high energies, iv) the physical mechanisms responsible for keeping the solar atmosphere much hotter than the solar surface (atmospheric heating), v) the evolution and topology of the global coronal magnetic field, vi) the coupling of the 3 distinct magnetospheric MHD waves and the physics of the coupling of planetary magnetospheres to their ionospheres. These phenomena obey physical laws that can be expressed as 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 requires a kinetic (particle) description, while many of the other 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.A very important research tool is 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 is important not only for the Sun, solar-like stars and space weather, but also for understanding such 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.