Earth Loses Magnetism

BBC ^ | 1-1-2004 | Molly Bently

[RightWhale]

what would cause it to reverse polarity under the water-vapor hypothesis?

Answer that for any hypothesis and win at least the Nobel.

Are there dipoles in the sun?

No, but due to ionization it doesn't need dipoles. The sun can generate mag fields just by churning ordinary electrical fields.

[r9etb]

Once again, I assume that if you allow molten ferrous material to mingle long enough, the atoms will align themselves to each other. Add to that the complex flow patterns resulting from convection and the earth's rotation.....and all bets are off.

Couple the magnetic field degradation with the fact that there hasn't been a leap second for five years (which is odd), and you've got the makings of a pretty interesting theory.

[inquest]

But at least with the core-convection hypothesis there's at least a somewhat plausible explanation, namely that the gyres change direction -or- perhaps that the strength of one gyre overcomes the strength of the other rotating in the opposite direction, and thus its field becomes the dominant field.

[RightWhale]

It seems like, and this is a gut feeling, core convection would be too slow and too stable to change quickly enough to correspond with fluctuations and known reversals in the magfield. Something more mobile would be needed. Something that can change quickly and often.

[inquest]

What about the second possibility I raised? It appears that there are at least two main gyres circulating inside the globe in opposite directions from each other. That would explain why at the crust is splitting in two directions at the mid-Atlantic ridge. If they're moving in opposite directions, then the fields they're generating would largely cancel each other out, unless one is a bit stronger than the other. So all it would take for a reversal of polarity would be a change in the relative strength of the two gyres, so that the other one becomes dominant.

[RightWhale]

The problem I have with that is that the material would be molten and electrically conductive, and so would lack a net electrical charge and also lack dipoles set in crystalline structure. Magnets are made of solid-state material or moving charge fields. There would be no mechanism to generate a magfield.

[XBob]

54 - "Only when an outside magnetic field is imposed do the atomic fields line up, which enables iron to "transmit" magnetism that's applied to it."

Magnetizable materials can also be magnetized/demagnetized with a sharp blow.

For example, you can magnetize a screw driver by wrapping a wire around it and briefly touching the wire between the poles of your car battery.

You can also drop a magnet onto a hard surface eg concrete floor, and it will demagnatize, and on occasion a non-magetized item will magnetize. (I have this happen, but have no idea how to control it, which way it goes)

[SunkenCiv]

Note: this topic is from 1/01/2004 .

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