Geomagnetic equator

The geomagnetic equator is the great circle on Earth’s surface midway between the geomagnetic poles, the poles of the centered dipole that best fits the main field. It does not coincide with the geographic equator and differs again from the magnetic dip equator, or aclinic line, where the magnetic inclination is zero and a freely suspended needle lies horizontal. Dip increases toward the magnetic poles and is zero along the dip equator, which matters for compass behavior because the horizontal field that drives the card weakens at high dip. The pattern is mapped by the World Magnetic Model.