Earth's Magnetic Field

[HydrogenBond]

A potential problem has arisen for the current earth's iron core theory and its magnetic field. It has to do with seismic evidence that demonstrated that seismic waves travel faster north-south (poles) than they do east-west (equator). This seismic speed anomaly is much faster than what should be predicted from the shape of the earth (bulges at the equator) and the crustal thickness differences N-S and E-W. What this data suggests is that the solid iron core is thicker north-south and stretches out toward the poles. It also suggests the solid core is thinner at the equator.

 

Here is the problem. If the solid iron core is due to the maximum heat and pressure within the center of the earth, why would it be thicker where the highest thermal gradient is (poles). The entire earth is also flattened (N-S), so there should be less gravitational pressure N-S. The paradox is less pressure and lower temperature making more solid iron core? A possible way around this is to explain the odd geometry being due to more inner solid core heat flowing toward the poles, making more solid iron N-S. Maybe the temperature is more important than gravitational pressure.

 

If we run with this proven seismic solid core geometry, the stretched out solid core closer to the coldest parts of the earth (poles), should result in the maximum thermal convection occurring within the liquid iron core that is located between the core and the poles. This should cause the earth's magnetic field to be orientated with the equator instead of lining up in its current orientation N-S (right hand rule).

 

In other words, the thermal convection should follow the current magnetic field direction, from core to the poles and then to the equator, with convections eddies forming along the way, similar to the high and low pressure circulations of the surface. But the direction of a magnetic field is perpendicular to the current. The iron core theory implies that the primary magnetic field should be running equatorially as it follows the primary convection from the poles toward the equator.

 

One might explain this with the linear convection toward the poles spinning with the earth's rotation. This spiralling will put the magnetic field in the proper observed orientation. However, the earth does not reverse rotation when the field reverses. The way around this is that the core's thermal convection, although traveling both N and S, will slant somewhat toward the pole that is colder. With the north polar ice cap melting, the south pole his beginning to have a higher thermal gradient. This means that more net core convection will head south reversing the magnetic field. In other words, the spin of the earth stays the same, but the primary convection direction will periodically reverse, reversing the field.