A PhD in Astrophysical and Geophysical Fluids?
The Astrophysical and Geophysical Fluids group has a large number of current research students and postdoctoral research associates and is a lively place to undertake research.
We are actively seeking students who are interested in undertaking research and have a number of possible projects in a wide range of fields — a brief description of some projects and the general area of research is included below. For more technical descriptions of the research we undertake, follow the links to the research areas.
Solar Dynamo Theory
- The Fast Dynamo problem.
How does a dynamo work at extreme parameter values? Diffusive effects are crucial for dynamos to work, yet they should not so large that the field diffuses away before it can be generated. The fast dynamo problem concerns the behaviour of dynamos when diffusive effects are small (as for astrophysical bodies). The problem is interesting mathematically as it involves singular perturbation theory and important astrophysically. - The large-scale dynamo problem.
Turbulent flows exist on a wide range of spatial scales in the Sun. Yet the magnetic field has an ordered structure with the eleven year sunspot cycle. How does this order emerge from the underlying turbulence. The generation of mean magnetic fields in astrophysical objects is a subtle process incorporating themes from turbulence theory. Both analytical and state-of-the-art computational techniques are required to make progress here.
MHD Experiments
- Taylor-Couette flow.
The flow between two concentric, differentially rotating cylinders is known as Taylor-Couette flow, and is one of the oldest problems in classical fluid dynamics. Despite this, there are still interesting questions to be addressed, particularly if the fluid is taken to be electrically conducting, and a magnetic field is externally imposed. In this case many new phenomena emerge that have no counterpart in the nonmagnetic problem. - Spherical Couette flow.
Spherical Couette flow is the flow between two concentric, differentially rotating spheres, and has much in common with the cylindrical Taylor-Couette problem described above. However, the different geometry also gives rise to new effects that have no analog in the cylindrical case.
Planetary Dynamos
- Convection in rotating magnetic systems.
Convection is believed to be the fundamental driving mechanism that generates planetary magnetism. Studying convection in such systems is therefore an important part of understanding planetary dynamos. The Earth has a fluid outer core (radius 3480 km) surrounding a solid inner core (radius 1220 km). Theory, and laboratory experiments, indicate that convection inside the tangent cylinder that just touches the inner core has a very different form to convection outside the tangent cylinder. This is a result of the rapid rotation. The project would explore the two different types of convection occurring in these regions, and how they couple together. - Dynamo models for giant planets.
Numerical solutions of the dynamo equations have successfully reproduced many of the observed features of the geomagnetic field. The aim of this project would be to adapt these codes which have been used for the geodynamo to model magnetic fields in Jupiter and Saturn. The structure of the field is quite well-known, but the conditions in the interior (e.g. the electrical conductivity) of these planets are much more uncertain. The idea would be to try out a range of simple possible models for the interior structure to see which gave magnetic fields that match the actual fields of these planets.