Earth's N and S magnetic poles "wander independently of each other and are not at exactly opposite positions on the globe" [from WIKI's "Earth's magnetic field"]. Can these independent motions be consistent with the supposed "dynamo effect" from electric currents of a liquid outer core? Can Earth's spheroidal shape be a factor?
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Well, Earth does not have a giant bar magnet inside, the outer core is an giant mass of conductive fluid in a complex motion guided by magnetohydrodynamics -- the problem is complicated enough to be unsolvable analytically and really gives no hope of simple solution. So one should rather think of a geomagnetic field which currently happens to be close to a dipole field, thus producing an illusion of poles. |
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Yes. If the earths magnetic field was strictly a dipole field cenetered at the center of the core then they the poles would have to be perfectly symmetric to each other. But the field is much more complicated than that. If you think of the field as being composed of spherical harmonics, you will see that the higher order harmonics fall off faster as a function of radius, so the terms higher than dipole aren't all that strong at the surface, but they are not zero, they so affect the local fields, and can skew the location of the "pole". spherical harmonics |
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