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Phil Livermore

It is a familiar concept that the Earth's magnetic field is predominately dipolar and aligned with the rotation axis. Yet despite huge advances in numerical geodynamo models, a full understanding of even this most basic of features remains out of reach.

My thesis focussed on the ability of simplified models, so-called kinematic dynamos, to help explain the large-scale field field structure. It has been well known since the 1930's of the impossibility of indefinitely maintaining a purely axisymmetric field, a first approximation to the geomagnetic field, by a dynamo mechanism.

However, by using techniques developed in the hydrodynamic community to understand transition to turbulence, I was able to show that on finite timescales relevant to the dynamics of the core that the generation of these fields was not only possible, but in general preferable to other field symmetries. In addition, the associated dynamo mechanism only depended on the large-scale features of the flow and can easily be understood in physical terms.

Currently a postdoc at the department of applied mathematics, Leeds University, I am investigating some of the fundamental mathematical issues associated with how turbulent, rather than well behaved laminar flows, can generate magnetic fields in planets and stars.
Since the 1960's, the popular "mean-field" theory based on the twisting effects of rotating turbulent flows on magnetic fields has been widely used and indeed has met with considerable success. However, certain fundamental aspects still remain poorly understood;  using carefully thought out test-cases, these can be scrutinised in isolation and thus we can identify in what regimes, if any, they are valid.

 ( Jan 2007)