The Earth's magnetic field reverses itself every 100,000 years or so, without respect this periodicity. This magnetic field (geodynamo) is produced by the movements of the alloys of iron and nickel in the molten liquid portion of the core of the Earth. According to geophysicists from the CNRS and the Institut de Physique du Globe, these irregularities are related to changes in the distribution of continents over the last 300 million years. The mantle rock Earth floats on the core of iron and nickel whose upper part is liquid. The magnetic field, causing the Earth's magnetosphere varies but slightly over long periods, it is reversed. There are over 780 000 years, a compass would have pointed to the South Pole. Researchers are studying these mechanisms in laboratory inversions that appear to be chaotic and stochastic (under the random). The study of geomagnetic records of the Earth does not really show the frequency of inversions, 100, 000 years of quiet periods, without inversion, can last 10 million years.
Image: Reversal of the Earth's magnetic field according to Hubert Reeves: what impact on us or nature?
Eccentricity and magnetic field
The eccentricity of the orbit of the planet would have an effect on the fluctuations of the angle and intensity of the geomagnetic field. This was said Toshitsugu Yamazaki and Oda Hirokuni, scientists from the Geological Survey of Japan. Earth's magnetic field is generated by the movements of liquid metal core, the deep layers of the Earth. By studying the long-term variations of the magnetic field, the two researchers examined the magnetic properties of a column of marine sediments, 42 meters long, deposited over a period of 2.25 million years. This enabled them to establish the intensity and direction of the geomagnetic field change over a cycle lasting 100,000 years. The eccentricity measures the deviation of the Earth's orbit from a circular orbit.
It ranges from 0 for a circular orbit at 1 for a highly elliptical orbit. But the eccentricity of Earth's orbit varies between 0 and 0.06 every 100,000 years.
Scientists are trying to understand how works the magnetic field. It seems that the geomagnetic field of the Earth is generated by interactions between the inner core and outer creating a giant dynamo. It is this that generates a strong magnetic field and stable. Lines of the picture are against the magnetic flux which flow from south pole of the core and return to the sphere from the north pole. In the earth's core, the currents of the solid inner core of the Earth heat the liquid outer core creating currents of particles around of the metal in fusion which rise and descend slowly. Under the effect of the rotation of the earth this currents turn themselves creating the magnetic field which flows to the surface and extends into the space. The Earth cooled slowly and when it will lost its internal heat, the liquid core will solidify and currents will stop flowing. Mars has no global magnetic field but region sparsely magnetized.
Measurements made on samples of Martian meteorites have shown that Mars has lost its magnetic field, because during the first 50 million years Mars had a strong magnetic field. Scientists do not know what has caused the disappearance of the Martian magnetic field. Exposed to solar winds Mars became the barren red planet we know today. Mars 2 times smaller than the Earth has cooled faster and dynamo stopped signing the death warrant of the planet.
Image: Lines of the picture represent the magnetic flux that flow from south pole of the core and return to the sphere from the magnetic north pole.