The secular variation of the geomagnetic refers to the changes of the Earth’s magnetic field on short time scales (annual to decadal). The rate of secular variation has been found to be not constant over the surface of the Earth, specifically in the Pacific hemisphere there is very little secular variation at all. One classical explanation of requires parts of the lower mantle to have a very high electrical conductivity. This high conductivity would screen out any quickly time varying components of the magnetic field, reducing the observed secular variation. Unfortunately, for the screening effect to work an unrealistically high conductance is required in the mantle, which is incompatible with constraints placed by the angular momentum budget of the Earth.