Vogt and Glassmeier derived magnetic field equations and magnetic equators for three symmetric quadrupole topologies (Figure 1) and demonstrated that magnetospheric plasma dynamics could behave quite differently during a pole reversal than during a normal dipole-dominated magnetosphere.

It may fall to 10 percent of the present-day strength and have magnetic poles at the equator or even the simultaneous existence of multiple "north" and "south" magnetic poles.

The detailed behaviour of the magnetic field during a polarity transition is described as well as the more recently observed phenomenon of excursions of the field or aborted reversals. Physical and mechanical models of the geodynamo are examined in some detail in so far as they may affect reversals.

As a matter of geological record, the Earth's magnetic field has undergone numerous reversals of polarity. We can see this in the magnetic patterns found in volcanic rocks, especially those recovered from the ocean floors.

During this geomagnetic reversal, the Earth’s magnetic field gradually weakens, flips in polarity, and then gradually strengthens again. On average, pole reversals occur every 200,000 to 300,000 years.