Solar and Magnetospheric Magnetohydrodynamics and Plasmas: Theory and Application

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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.