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Planet cores precession

by Andre
Tags: cores, planet, precession
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Andre
#1
Nov10-03, 01:42 PM
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We know that the Earth is precessing.

http://www.crystalinks.com/precession.html

The Earth's rotation axis is not fixed in space. Like a rotating toy top, the direction of the rotation axis executes a slow precession with period of 26,000 years for the entire ecliptic of our planetary bodies to travel around our sun, a trip of 360 degrees. Each one of the 12 signs of the zodiac takes about 2100 years for our solar system to pass through. Every 72 years we actually move backward 1 degree. After 2100 years we move out of one age and into another. ....

Because of the gravitational forces of the sun and the moon on the equatorial bulge of the rotating earth, taking into accountt the angle of 23.439 degrees between the rotation axis of the earth and the normal vector to the plane in which the earth orbits around the sun (the ecliptic), the rotation axis moves with respect to a space-fixed reference frame.
We also know that the Earth has a fluid outer core and a solid inner core. How would the core(s) react on that precession movement?
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Andre
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Nov11-03, 12:15 PM
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Come on. no deep thought on this one?[zz)]

Would the solid core spin axis just follow the mantle in the precession, because the precession also acts on the core, or not?

Would the Earth magnetic field has anything to do with it, would the magnetic field -thought to be generated in the liquid outer core- stabilize the spin axis of solid inner core, to maintain alignment with the mantle spin axis?

Or would the liquid outer core act as a torque converter as in a automatic transmission gearbox and stabilize the spin axis of the inner core?

Suppose that stabilizing mechanisms would fail, would the inner core spin axis lose alignment with the mantle spin axis? What would we the result of that?
Nereid
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Nov19-03, 08:53 PM
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How do the inner and outer cores interact? How strong are the various linkages? What is the characteristic scale of relative motion between the two - both in time and 'length'? How fast does material - in convective motion in the outer core - move (relative to some rotating frame)?

Andre
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Dec20-03, 08:07 AM
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Planet cores precession

Sorry Nereid, I've overlooked this thread being seemingly not interesting. I think however that these elements have the highest possible impact on geology and ultimately on life itself.

Those questions you pose can never be answered accurately. However some rough modelling may be possible.

Again. When the spin axis of the Earth mantle is performing a conical presession, we would assume the solid Earth core to follow. However it has to be forced to follow, since it's own precession logic must have totally different parameters. This stabilisation process could be mechanical, where the fluid outer core has enough friction to transfer the required forces. It could also be magnetic, where the magnetic field generated in the outer core keeps the magnetic field of the solid inner core aligned. It could be both. Nobody knows.

However the Earth magnetic field is collapsing frequently as the recent paleomagnetic map shows:



Would the magnetic coupling between inner and outer core be affected by those paleomagnetic excursions?

Another factor is the angular momentum of the solid inner core. If the inner earth has a tendency to cool, as a reaction the solid inner core would grow in size, increasing it's angular momentum to the fifth power of its radius. This would require more and more force to keep the inner core spin axis aligned with the mantel.

But, what would happen if the spin axis of the solid inner core would not follow any longer, because the stability mechanism is no longer strong enough to correct the different precession tendency?


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