Personally I was surprised by how much we do not know about the mechanism that creates Earth's magnetic field or the reason for the reversals.
There are two main theories explaining Earth's magnetic field:
- Dynamo Theory: states Earth's magnetic field is caused by the convection of conductive fluids within Earth's core, most likely liquid iron. Apparently the reversals are an "inherent aspect of dynamo theory"-Wikipedia. What ever that means. What I do know is that the upper crust of Earth prevents the convection of the molten iron. However Dynamo Theory is the most popular theory of the moment.
-- geomagnetic excursions: Some scientists believe that a change in reversal is caused by an external impact such as a comet collision. They also figure that the magnetic field must be "stopped" and then turned back on.
- Georeactor Theory: Fixes some of the problems with dynamo theory because it does not require convection. fusion reactions deep in the core are the cause of the magnetic field. This theory was originally designed to explain the magnetic fields of outer planets such as Jupiter and Saturn. Because extreme pressures and temperatures are needed to create fusion many scientists are skeptical that the necessary conditions could be obtained in a planet Earth's size. This theory has much less support than dynamo theory for this reason.
What does have strong evidence is that the magnetic field has reversed before: http://en.wikipedia.org/wiki/Geomagneti ... ast_fields Field reversals can be detected by studying the magnetization of iron rich minerals from different time periods, since these minerals are influenced by the ambient magnetic field of the time.
So we know that their is a field reversal but we don't know why there is a reversal?
- Magnetic Portals: Recently (by recently I mean October of last year) it was discovered that the magnetic fields of the sun and Earth connect about every eight minutes forming a sort of magnetic portal (about as wide as Earth allowing high energy particles to cruse through energizing Earth's Magnetic field. As of know no one really knows what causes them, but its to early to be certain but could these FTE's (flux transfer events as they are being called) be the cause of our pole reversals?