There were many models (like Barnett, magnetic matter inclusions ones) to explain the Earth magnetism. But there were failed. The Earth magnetic field was reoriented some times. What are reasons of it? How is about today approved theory of the Earth magnetism?
The core of the Earth, such as the other planets, is, according to current theory, a giant magnetohydrodynamic dynamo that generates the earth's magnetic field. This phenomenon is due to the convective movements of the outer core, composed of iron and nickel alloys, and induced electric currents.
It is generally believed that the terrestrial dynamo stops, either spontaneously or as a result of a triggering event, and that after a transition period (1,000 to 10,000 years) it starts again with the pole North up or down. When the north reappears in the opposite direction, it is an inversion. When it returns to its initial position, it is a geomagnetic excursion.
There are other models to explain this phenomenon. Moreover, in all cases, this movement is accompanied by a marked weakening of the value of the field.
Some scientists think that geomagnetic inversions are triggered by events that disrupt the flow of the Earth's core.
These events could be of external origin, such as cosmic or internal impact, such as the arrival of continental slabs carried into the mantle by the action of plate tectonics in subduction zones or the appearance of new plumes at The boundary of the kernel-mantle boundary.
Simulation works are carried out by various research teams and the question remains open!
Venus, with quite similar material conditions is without a magnetic field. The main difference with the Earth is that it rotates much more slowly, but the origin of the magnetic field of the Earth is not yet known. On one hand, the temperature is much higher than the critical temperature of ferromagnetic phases and on the other hand the a current of electric plasma is difficult to understand (by inertia) how can stop and invert its motion.
Can here tomography methods (different inverse electromagnetic problems) of the Earth magnetosphere (from satellites view) be applied? There are many tomographies: magnetic resonance, electric impedance, etc. For example inverse Laplace transform is also now used in the oil search by NMR. How about the view of magnetic moments distribution inside the Earth? Is it known? Is it solvable problem (you already gave, I think, the answer, but by the way)?
The experimental measurements depend strongly of the origen of such magnetism. If it is due to a current it is very difficult to "see" as if it were due to a spin order magnetic material. I'm afraid that we are in the first situation and I think that is really difficult to detect.
Do you know about quantum nuclear magnetic resonance gyroscopes used in satellites? Nuclear magnetic moments precesses around the Earth magnetic field. That is old story. I am sure that it is very simple to make a 3D map of the Earth magnetosphere by quantum magnetometers. Please clarify me if I did not understand you. If I am right why did we not do it. Just no money ..:)?
Dear Anatoly,
NMR is associated to the magnetism of the nucleus but we here are speaking on a plasma of charged particles which moves producing a current. This by Ampere's law gives a magnetic field, therefore the NMR is not a good technique for measuring the magnetism of the Earth.
Maybe you are right. But there are quantum satellite gyroscopes (NMR gyroscopes) (I was learned they was 50 years ago). How do they work in the situation you painted?
Dear Anatoly,
I don't know how the gyroscopes work, in principle what they must do is to fix the direction and to keep during the trajectory.
Perhaps what could be interesting is to do during all the year very accurate measures of the Earth magnetic field and to see if the small variations are correlated with any other variable.
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