The Eccentric Dipole (ED) model of Earth’s magnetic field is an attempt to get a better approximation Earth’s geomagnetic pole locations compared to the simple dipole (i.e. bar magnet) approximation of the\u00a0centered dipole approach<\/a>. The eccentric dipole approximation acknowledges that the field is slightly offset from the Earth’s spin axis although it retains a dipolar character. The eccentric dipole model uses the first 8 terms of the\u00a0spherical harmonic expansion<\/a>\u00a0(i.e. the Gauss coefficients up to degree 2) of the International Geomagnetic Reference Field (IGRF). These are the g1<\/sub>0<\/sup>, g1<\/sub>1<\/sup>, h1<\/sub>1<\/sup>, g2<\/sub>0<\/sup>, g2<\/sub>1<\/sup>, h2<\/sub>1<\/sup>, g2<\/sub>2<\/sup>, h2<\/sub>2<\/sup>\u00a0terms. Two different types of poles can be calculated: an eccentric dipole axial pole which is where the axis of the dipole intersects the Earth’s surface and\u00a0an eccentric dipole ‘dip’ pole<\/a>\u00a0where the field is vertical at Earth’s surface. See Fraser-Smith, (1987) for a full explanation. See also background information on spherical harmonics on\u00a0the Space Environment Information System\u00a0<\/a>operated by the European Space Agency.<\/p>\n\t\t\t\t\n\t\t\t\t The following table lists the calculated Eccentric Dipole (ED) axial pole and dip pole locations for the North Magnetic Pole (NMP). Epochs 1600 through 1800 are from Barraclough (1974) the remainder are calculated from the DGRF\/IGRF models.<\/p>\n\n![\"Geomagnetic](\"https:\/\/website.whoi.edu\/deeptow\/wp-content\/uploads\/sites\/66\/2023\/08\/northpole_ed-scaled.jpg\" "\\"northpole_ed\\"")
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![an eccentric dipole ‘dip’ pole<\/a>\u00a0where the field is vertical at Earth’s surface. See Fraser-Smith, (1987) for a full explanation. See also background information on spherical harmonics on\u00a0](\"https:\/\/website.whoi.edu\/deeptow\/wp-content\/uploads\/sites\/66\/2023\/08\/northpole_eddip-scaled.jpg\"){kind=link}