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Posted: Jun 4 2006, 02:30 PM
Group: Power Member
Joined: 11-August 05
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The current theory of the earth's magnetic field is connected to magneto-dynamic affects caused by convention in the fluid region of the earth's iron composite core. Simulations using this theory have been able to demonstrate the natural reversal of the earth's magnetic field in 100K year (more or less) cycles. This gives reasonable proof of the theory.
Unfortunately there are some observational anomalies that can not be simulated with core material convection alone. I would like to list a few for comment.
1.) The axis of the magnetic North and South Poles does not coincide with the geographical axis of the Earth's rotation, being subject to apparently random drifts of hundreds of kilometers from the Geographic Poles, although roughly around them. At the present time there appears to be a generally westward movement, which seems to have been going on for several centuries.
2.) A hypothetical line drawn from one magnetic pole to the other does not actually pass through the Earth's center.
3.) Magnetic fields from past geological epochs are sometimes preserved in magnetizable strata and rocks such as lava as they cool below their Curie points, and their intensities can be measured. A study was made of intermittently produced Miocene lava formations at Steen's Mountain, Oregon, USA, which gave a very detailed picture of both the intensity and directional changes which occurred during a magnetic reversal. The complete reversal took about 4500 years and the average magnetic field at the surface fell to about 20% of normal during the change. The transitional field was typically non-axisymmetric and there was much meandering, even crossing the equator three times. Three geomagnetic impulses occurred which corresponded to high rates of change of the field. The angular rates of change were approximately 50 +/- 20 degrees per year.
4.) On a much more rapid scale, around about 1969, a so-called 'jerk' occurred in the geomagnetic field, almost synchronously over the whole surface of the earth. It took place in less than 2 years.
5.) To increase the complexity even more, the existence of more than 1 North/South magnetic pole system is known. A number of additional magnetic fields have been measured accounting for about 10 % of the total magnetic field intensity of the Earth.
6.) In two regions of the boundary between the earth's core and the overlying mantle, researchers detected a reversed magnetic field. In a section lying beneath the southern tip of Africa, the magnetic field points toward the center of the Earth opposite to the dominant outward-pointing field of the Southern Hemisphere. A second congregation of reversed-flux patches exists near the North Pole.
Such radical changes in direction, position, and intensity in short periods are not dynamically consistent with theories which rely on the rotation of heavy metallic layers in the Earth's interior.
Posted: Jun 4 2006, 02:54 PM
Joined: 26-April 05
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sorry, MDT -
You're leaving out some VERY IMPORTANT pieces of the puzzle. First of all, I'd like very much to see your math.
Secondly, I strongly suspect that if you had considered the Earth's precession in your calculations, you would see a Fourier transform emerge, which would couple at least partially to the roving B field we have seen over the years.
Thirdly, you would have had to have coupled w/ the variable density and variable shape of the earth's fluid iron core (which are currently impossible to calculate, as we have no way of mapping the variable density or shape).
Fourth, the liquid itself has its own internal B field (as does any ferromagnetic material), can easily couple w/ the exterior one we observe. It's made MUCH more complex by the fact that, since it's a liquid, that internal B field is constantly variable. For example, chi (magnetic susceptibility) or dM/dV is NOT uniform in each axis you choose in a perturbed liquid and SURELY not for one that likely folds in on itself.
If I were so inclined to think about a problem like this (which I'm not - there are much sexier problems out there to think about - but go for it if it floats your boat!), I would at least start by seeing how and/or whether the changing B fields conform to low-rank Legendre polynomials (which they probably do).
- angrily spinning my solids (it's sunday and I have to go to the lab and ck that I haven't exploded the magnet)