Introduction

There are many problems in the geosciences that rely on the ability to accurately determine the magnetic properties of minerals and the stability of the palaeomagnetic recordings that they contain. For example, the investigation of the behaviour of the geomagnetic field depends largely on the observed field variations on or above the Earths surface. Temporal records of direct observations stretch back less than two hundred years, and so a more detailed analysis is dependent of ancient recordings made in rocks as they are formed. Geological interpretation of the directional recordings of the ancient field led to the discovery, over 50 years ago, that the Earths oceanic and continental plates are continuously moving. Today, a more thorough understanding of magnetic mineralogy enables a detailed analysis of not only of fine scale continental block motions and rotations, but also emplacement temperatures and thermo-temporal history of the rocks to be determined. A further, but my no means only, example is that magnetic mineralogy is frequently used as a proxy for determining palaeoclimate variations.

All these applications depend on an understanding of how the magnetic properties of minerals change with the mineral microstructure, chemistry, grain geometry and inter-grain magnetic interactions. The complexity and diversity of naturally occurring magnetic minerals makes the numerical micromagnetic problem a much more difficult task than that applied to the generally more ideal man-made recording media. The increasing sophistication of environmental-magnetic investigations relies on a high-fidelity magnetic re-coding processes occurring in natural magnetic mineral systems. Yet our understanding of the fundamental processes that enable common magnetic minerals to record the local geomagnetic field’s direction and intensity and to retain this information over geological time scales is far from complete. A much better understanding of the recording process in natural materials is required in order to assess the reliability of rock-magnetic recordings.

Equilibrium magnetic domain structures are determined by integration of the Landau-Lifshitz-Gilbert equation of motion. Finite element methods are the preferred technique when dealing with irregular geometries since magnetic domain structures are sensitive to the accuracy with which grain geometries can be modelled. The code, MicroMag, before the dCSE existed as a serial code (written in Fortran90). Some initial work had been undertaken in investigating methods of parallelisation. This was the basis for the work-plan submitted as part of the dCSE proposal.