Consolidated Grant in Solar and Planetary Studies: Department of Applied Mathematics, University of Leeds

Many astrophysical phenomena involve the complex interaction between magnetic fields, rotation and turbulent fluid flows. We will undertake a systematic and integrated programme of research to investigate this interaction in a variety of contexts in solar system and planetary sciences. We shall utilise a combination of analytical and numerical techniques (including the application of cutting edge numerical algorithms optimised for use on massively parallel machines) to gain an understanding of such phenomena.

We propose to investigate the following specific problems:

(1) On the Sun, magnetic field is observed to exist over a range of spatial and temporal scales, from the large and long-lived to the small and short-lived. Furthermore, the convection at the solar surface also has a range of scales, from supergranules (which are about 20,000 km across) down to granules (about 1000 km). A new anelastic code has been developed in Leeds, and we will use this to explore the interaction between the convection and the magnetic fields to explain these observed ranges in scale. We will address the important issue of whether the observed small-scale magnetic field is broken-down large-scale field, or whether it is generated afresh by a small-scale dynamo. We shall also explore the role of the near-surface shear layer to see how it affects the solar magnetic field just below the photosphere.

(2) A key observational discovery in solar physics was the identification of the "solar tachocline", a thin region of strong velocity shear, deep in the Sun, sandwiched between the convective and radiative zones. Recent satellite observations of the Sun have revealed new short period activity cycles in addition to the 11 year activity cycle. Long term observations of bright points in the corona have revealed slow waves. These waves and activity cycles most likely arise in the tachocline. We will explore what types of waves the tachocline can support, and how they develop in the nonlinear regime. This will enable us to discover if these new observations can be understood in terms of tachocline dynamics, and how these signals in the deep interior are transmitted to the solar surface.

(3) The nature and strength of the magnetic field in the radiative interior below the tachocline is a major unknown of solar research. We will explore a mechanism known as magnetic buoyancy, by which magnetic fields rise upwards. This is known to be important nearer the surface, but it might also play a role in the deepest regions of the Sun. There is an analogy between magnetic buoyancy and double diffusive convection, which occurs in our oceans. It has recently been discovered that by forming density layers, the transport of heat and salt in the ocean can be much enhanced. By studying three-dimensional, nonlinear models to investigate this layering process in the magnetic context, we will explore whether such layering can occur in the deep solar interior. This will provide important new constraints on the magnetic field in the solar radiative zone.

(4) The Juno space mission has sent back stunning pictures of Jupiter's surface, and we now also have much more accurate data about Jupiter's magnetic field and its gravity field. The gravity field data has shown that the strong winds seen at the surface of Jupiter penetrate deep into the interior of the planet. We also have similar data for Saturn from the Cassini Grand Finale, when the Cassini probe dived into Saturn, recording close up data just before it was swallowed up. We now plan to assimilate this accurate data into our dynamo models for giant planets, and hence constrain interior models in a way that has hitherto not been possible. We aim to discover if Jupiter has a dense, compact core or a large, dilute core as recently suggested. We will also explore whether the deep winds predicted by our dynamo models are consistent with the observed winds.

Our astrophysical fluid dynamics and MHD group has a good track record of actively engaging with the public about our research. We have given talks in Schools, and given radio interviews about our latest results. Several of these interviews relate directly to the research projects for which we are now requesting funding. The University of Leeds has built up good contacts with schools, and also maintains good relationships with broadcasters, so we will be in a strong position to maintain these activities over the next consolidated grant round. Particularly important is that we always take advantage of opportunities for disseminating our results as they occur, and sometimes these opportunities require action from us at quite short notice. We will also continue to involve our postdocs and PhD students with public engagement opportunities as they arise. For example, we encourage young researchers to participate in our radio interviews, which has resulted in a great benefit to their development, as well as helping to disseminate our research to the public. Our PhD students also regularly participate in Science Week.

Our research also has potential impact in the field of space weather, as several of our projects relate to solar activity, and in particular short term solar activity. Space weather is an area of growing importance, as our global communications and monitoring capabilities increasingly depend on satellites. The UK satellite industry has been identified by the Institution of Engineering and Technology as one of the six sectors that are likely to create the biggest opportunities for the next generation of British engineers and technicians. Satellites are vulnerable to surges in solar activity, which can lead to harmful electrical and magnetic disturbances in the Earth's environment, so there is world-wide interest in predicting when surges are likely to happen. This is motivating studies by ourselves and our collaborators at the High Altitude Observatory in Boulder, Colorado, to understand more clearly how these activity surges arise.

Our group is also active in Knowledge Exchange. Members of the group regularly give lectures at graduate summer and winter schools, not just in the UK but all over the world. We see this as an important activity. It can help build up the skills that the next generation of young scientists will need if they are to successfully tackle the scientific challenges in solar and planetary science that lie ahead. We will continue to actively seek opportunities for disseminating our knowledge, and we will deliver in this key activity over the next grant period.

STFC recognizes three ways of maximizing the impact of its investment for the benefit of the United Kingdom and its people: world-class research, world-class innovation and world-class skills. We believe our work qualifies on all three counts: in terms of the astrophysical research itself, the innovation of fundamentally new numerical methods (which may also be useful in areas outside astrophysics), and the training of Postdocs and PhD students in utilizing high-performance computing skills (which again are enormously useful in many areas outside astrophysics).