EarthRef.org Reference Database (ERR) -- Campbell 2004

A special session, Decay of the Main Field, was held at the AGU Fall Meeting in San Francisco, California, 11 December 2003. Two of the presentation topics were the recent main dipole field decay indicated by the International Geomagnetic Field (IGRF) representation and the unique properties of the second and third field harmonics obtained from the IGRF. The Earth's dipole field is certainly decaying, but neither at the strength nor rate announced at the AGU meeting. And the higher harmonics of the IGRF are especially important for any calculation of the expected magnetic field at a location on the Earth's surface, but only for that purpose. The large second and third field harmonics mainly arise because of the offset of the Earth's main dipole field from the geographical center. A special session, Decay of the Main Field, was held at the AGU Fall Meeting in San Francisco, California, 11 December 2003. Two of the presentation topics were the recent main dipole field decay indicated by the International Geomagnetic Field (IGRF) representation and the unique properties of the second and third field harmonics obtained from the IGRF. The Earth's dipole field is certainly decaying, but neither at the strength nor rate announced at the AGU meeting. And the higher harmonics of the IGRF are especially important for any calculation of the expected magnetic field at a location on the Earth's surface, but only for that purpose. The large second and third field harmonics mainly arise because of the offset of the Earth's main dipole field from the geographical center.