The authors would also like to thank the numerous suppliers of observed magnetometer data, data providers include Lou Lanzerotti and Carol Maclennan at Lucent Technologies, David Boteler at the Geological Survey of Canada, the Cannopus Chain, the Measure Chain, the 210 Chain, the IMAGE Chain, the World Data Center for Geomagnetism in Kyoto, Japan, the LANL Magnetometer Chain, the SMALL Array, the Chi-Mag Array, and the CPMN & PI Chains.