Model derived geomagnetic poles
Geomagnetic field models can also define geomagnetic poles. The geomagnetic poles, or geocentric dipole, can be computed
from the first three Gauss coefficients from a main field model, such as the World Magnetic Model (WMM) or International
Geomagnetic Reference Field (IGRF). The WMM representation of the field includes a magnetic dipole at the center of the
Earth. This dipole defines an axis that intersects the Earth's surface at two antipodal points called geomagnetic poles.
Based on the WMM2010 coefficients for 2010.0 the geomagnetic north pole is at 72.21°W longitude and 80.08°N latitude,
and the geomagnetic south pole is at 107.79°E longitude and 80.08°S latitude. The axis of the dipole is currently
inclined at 9.98° to the Earth's rotation axis. The same dipole is the basis for the simple geomagnetic coordinate
system of geomagnetic latitude and longitude. Scientists, map makers and polar explorers have an interest in the
locations of the dip and geomagnetic poles. Although geomagnetic pole positions cannot be observed, they are arguably
of greater significance than the dip poles because the auroral ovals (approximate 5° latitude bands where the spectacular
aurora is likely visible) are closely centered on the geomagnetic poles. They are usually displaced slightly to the
night-side of the geomagnetic poles and greatly vary in size: bands of greatest activity occur between 15° and 25°
from the geomagnetic poles.
A software for computing the locations of geomagnetic pole is available here.
Movement of magnetic poles from 1590 to 2010
The magnetic poles or dip pole are computed from
all the Gauss coefficients using an iterative method. Magnetic poles derived in this fashion
are more closer to the experimentaly observed poles. Based
on the current WMM model, the 2010 location of the north magnetic pole
is 84.97°N and 132.35°W and the south magnetic pole is 64.42°S and 137.34°E.
The Google map below illustrates the movement of the magnetic poles during 1590 to 2010 derived from the GUFM
(1590 – 1980) and IGRF (1981 – 2010) models. The GUFM model (Jackson et al., 2000, Four centuries of geomagnetic
secular variation from historical records, Phil. Trans. Roy. Soc. Lond. A, 358, 957- 90.) covers the period 1590 -1990
and is based on ship log data. The path reflects the chaotic and independent movement of magnetic poles. For example,
the present rate of progression of the north magnetic pole (55 km/year) is significantly higher than that of the South Pole.