01Magnetic field of the Earth

Not only bodies, but also entire planets, may have a magnetic field. For this, defined conditions must be in place. The Earth also has a magnetic field that surrounds it. This principle is similar to that of the 'small' magnetic fields of electromagnetsor those surrounding ferromagnetic materials. Here too, movement must take place between charge carriers. Energy stored in the Earth's core acts as an energy source that is also responsible for the movement of the conducting material. In the case of our Earth, this is performed by the liquid outer part of the Earth's core that contains a high proportion of iron, and is therefore conductive.

The strong temperature differences in the Earth's core assure rotating movement in the liquid part of the core, causing induction to take place that causes the magnetic field around the Earth. The sequence of movements designated Geodynamo does not have to be very powerful in order to generate this field.

Another decisive aspect is that the core of the Earth rotates more rapidly than the Earth's mantle. There is speculation to the effect that, for this process, the impact of tidal forces exerted by Moon and Sun may have a decisive role to play, although clear-cut scientific confirmation of this has yet to be produced.

The fact that the geographic North Pole is, in physical terms, a magnetic South Pole, is now widely recognized. Furthermore, a distinction is made between the geographical, magnetic and geomagnetic Pole. The last of these is a theoretical pole point in the assumed magnetic field of the Earth, inclined at 11° to the axis of the Earth. The other magnetic poles are based on very specific calculations. In both cases however, these 'poles' are not at fixed locations, in contrast to the geographic Poles.

Some animals - unlike human beings - can perceive the magnetic field of the Earth and orient themselves with its help. The best known examples of this are migratory birds that change their habitat every year for defined seasonal periods. Typically, in the case of European migratory birds, they fly down to warmer climes to spend the winter.