Dynamics of Planetary Cores (Astrophysical and Geophysical Fluid Dynamics)
The interior of the Earth is divided into an iron core of radius 3,480km surrounded by the mantle. The mantle convects on a very slow timescale, giving rise to continental drift, but the iron core convects more rapidly. This core motion can now be detected by measuring the changes in the Earth's magnetic field, which is carried around by the moving fluid. Recently developed scientific techniques have greatly improved our understanding of core conditions, and this has made it possible to study the way the fluid moves and generates magnetic field. Numerical models, based on solutions of the fluid equations, have been remarkably successful. Many observed features of the geomagnetic field can be reproduced, even including surprising reversals of the whole dipole field. Building on that success, we are now trying to construct models of the dynamics of other planetary cores; some have strong magnetic fields like the Earth. Others, like Mars, had strong fields in the past, but for some reason the Martian dynamo stopped working at some point in its history. We wish to know why! The project would involve developing the techniques we are using to study the Earth's core so they can be used to study the conditions inside other planets.
Astrophysical and Geophysical Fluid Dynamics
The group in Leeds is one of the leading groups in the field of Astrophysical and Geophysical Fluid Dynamics, with international reputation in dynamo theory, astrophysical MHD and convection. The strength of the group is recognised by the award of several prizes and special fellowships. The group also holds one of the largest grants ever awarded to the University of Leeds. The nine permanent members of staff work with eighteen postdocs and postgraduate students.
The group is actively engaged in research in a wide-range of areas of astrophysical and geophysical fluid dynamics: from planetary dynamics (the geodynamo and planetary dynamos) through solar, stellar and galactic dynamics to highly compressible and relativistic dynamics on the largest scales. Magnetic fields are a strong theme, and the group is interested in how planets (like the Earth), stars (like the Sun), neutron stars, black holes and galaxies generate their magnetic fields through dynamo action. On the Sun, the well-known eleven-year sunspot cycle is a manifestation of the solar dynamo; indeed the solar magnetic field underlies all solar magnetic phenomena such as solar flares, coronal mass ejections and the solar wind. In the Earth, magnetic fields are generated by convection in the molten iron core, and it has recently become possible to solve the fundamental equations that govern the motion of fluids and the generation of magnetic fields, and successfully reproduce many of the observed features of the geomagnetic field. At the other end of the scale, magnetic fields are implicated in the formation of spectacular jets coming from neutron stars, black holes and galaxies. Without magnetic fields, the group has interests in waves and hydrodynamic instabilities in rotating stratified fluids, with applications to the Earth's atmosphere and ocean (and with application to other planets).