Solar and Magnetospheric Magnetohydrodynamics and Plasmas: Theory and Application

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.

While the main impact of the proposed research will undoubtedly be of academic in nature, there will also be significant economic and societal impact. De Moortel had an STFC IAA grant in 2016 to collaborate with scientists at Lockheed Martin on forward modelling of numerical experiments. The results have been used to help determine the specifications for instruments onboard a newly proposed satellite mission (MUSE), to be able to achieve the science goals. In July 2017, the proposed mission (on which De Moortel is now a Co-I) was selected by NASA for an 11-month, phase A, concept study ($1.25M). Mackay had STFC IAA grant funding in 2016 to develop an automated software package for the preparation, running and analysis of non-linear, force-free field simulations of active regions, where these simulations are driven directly from observed magnetograms. This has been carried out in collaboration with the MetOffice and the software was delivered to them in 2016.

The skills required for research in theoretical solar physics means that our group is continually producing people skilled in modelling, computational (& parallel computing) methods and visualisation techniques for non-academic professions. There is a universality of techniques required to solve cutting-edge scientific problems in MHD that means our group members are highly sought after. An example of inter-disciplinary research is given by the EU grant for "Model-based preclinical development of anti-tuberculosis combinations". Using computational techniques used in MHD research, work is being undertaken in understanding how to treat tuberculosis by using combinations of drugs.

Nearly 40 former group members have gone on to academic positions, over 55 former group members have flourishing careers outside academia. Thus, we are enhancing the UK research capacity as well as the knowledge and skills of businesses and organisations. Several former PhD students have joined the Atomic Weapons Establishment (Aldermaston) and GCHQ, where their computational skills are potentially improving national security. Former group members formed the scientific consultancy firm, Fluid Gravity Engineering and use their computational skills to solve a wide variety of problems, such as modelling the re-entry of space vehicles back into Earth's atmosphere. FGE are regular recruiters of our PhD students.

Our public lectures and presentations at various local and national science fairs have helped to increase public awareness in the importance of our research. The ready access to the latest images and movies of the solar atmosphere is extremely useful. When the public can actually see observations on their smart phones within seconds of the images being made, they are always excited. In another example, the group organised some street busking, and visited the Dundee Science Centre with solar outreach material during Maths Week Scotland 2017 (see e.g. https://twitter.com/SMTG_StAndrews/status/909062173426667522). Our visits to both primary and secondary schools have helped to enthuse students to study science, in general, and physics and mathematics, in particular. The annual Space Camp and Sutton Trust summer schools are particularly popular with primary and secondary pupils and help to encourage pupils to study STEM subjects. IDM was a co-organiser of a meeting between St Andrews academics and local head teachers (Jun 2017) to discuss how to facilitate outreach and interactions between academics and local schools.

On the academic impact front, we have organised many conferences over recent years (for example, SFTC Solar System Summer School 2016, BAMC and UKMHD March 2018) and are regularly members of SOCs. Our research has made an impact on the astronomy community with a recent Royal Astronomical Society award, the 2015 Chapman Medal to Hood.