Affiliation: | Geomagnetism unit, Institute of Geological Sciences, Murchinson House, West Mains Road, Edinburgh EH9 3LA;Department of Applied Mathematics and Computing Science, The University of Sheffeld, Sheffield S10 2TN;Department of Mathematics, university of Keele, Keele, Staffordshire ST5 5BG;Geomagnetism unit, Institute of Geological Sciences, Murchinson House, West Mains Road, Edinburgh EH9 3LA;Department of Mathematics, university of Keele, Keele, Staffordshire ST5 5BG |