What happens when the magnetic poles switch?

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Offline Yair Doza

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What happens when the magnetic poles switch?
« on: 23/03/2010 17:30:02 »
Yair Doza  asked the Naked Scientists:
   
Hi
 
I was wandering about the change in the magnetic pole. As I understand the core of our planet changes its rotation every ~80,000 years, causing the north and south pole to change.

For a period of time (hundred or thousands of years) there is no magnetic pole as the rotation slows down.

This raised two questions:

1 - Animals migrating that use the magnetic fields must go the wrong way after each change of the magnetic field. How do they survive? Surely the evolution to adapt to the new magnetic pole takes generations, but all the migratory organism would perish if they go north for the winter in the northern hemisphere.

2 - As I understand the magnetic field of Earth is creating Van Allen (?) belts that stop the damaging solar wind from reaching earth. What stops this wind when there is no magnetic field during the time it takes the poles to swap places?
 
Thanks

Yair Doza

What do you think?
« Last Edit: 23/03/2010 17:30:02 by _system »

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Offline Bass

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What happens when the magnetic poles switch?
« Reply #1 on: 23/03/2010 21:00:17 »
Welcome to the forum Yair

Your question contains a couple of common misconceptions:

1.  The magnetic field doesn't disappear, nor does rotation of the core slow down or stop.  Physical and computer models both show that it only takes small fluctuations in convection currents in the fluid outer core to change magnetic polarity. Most likely, there are several poles (four or more) during the reversal transition.

2.  Pole reversals probably happen over a span of several thousand years, in which the poles (however many) migrate around the earth.

3.  The magnetic field still exists during the transition.

One would suspect that migratory animals may be confused during the transition period.  However, there are no indications of massive extinctions during pole reversals- so either the transition is gradual enough for animals to adapt, or they have other means of navigating.

Since the field doesn't actually disappear, solar radiation will still be deflected.

JimBob was around for the past couple of reversals- so he can relate first-hand knowledge of the process. [;D]

Old enough to have a grandson
Slow enough to study rocks
Thirsty enough to find a pub

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Offline Geezer

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What happens when the magnetic poles switch?
« Reply #2 on: 23/03/2010 21:25:10 »

JimBob was around for the past couple of reversals- so he can relate first-hand knowledge of the process. [;D]



Bass, I think that would explain why JimBob is a wee bit disoriented.

http://www.thenakedscientists.com/forum/index.php?topic=30696.msg304579#msg304579
There ain'ta no sanity clause, and there ain'ta no centrifugal force Šther.

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Offline JimBob

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What happens when the magnetic poles switch?
« Reply #3 on: 24/03/2010 01:24:29 »
What?

Nurse please pass me my pills.
The mind is like a parachute. It works best when open.  -- A. Einstein

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Offline Geezer

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What happens when the magnetic poles switch?
« Reply #4 on: 24/03/2010 03:32:25 »
I keep telling you!

Ask for the screens first (sheesh!)
There ain'ta no sanity clause, and there ain'ta no centrifugal force Šther.

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Offline LeeE

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What happens when the magnetic poles switch?
« Reply #5 on: 24/03/2010 09:41:08 »
I believe that a small number of 'sub' magnetic poles already exist at various places around the Earth and I also seem to recall discussing these on this forum in the last year or so.  However, I've been unable to find any references to the sub-poles, or the map of them that I remember seeing, via a google search and neither could I find the forum thread via a quick search, so I might just be imagining it all.

Oh well  [???]
...And its claws are as big as cups, and for some reason it's got a tremendous fear of stamps! And Mrs Doyle was telling me it's got magnets on its tail, so if you're made out of metal it can attach itself to you! And instead of a mouth it's got four arses!

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Offline JimBob

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What happens when the magnetic poles switch?
« Reply #6 on: 24/03/2010 16:19:09 »
I am looking for it. I have been since I saw this post without any comments on it.
The mind is like a parachute. It works best when open.  -- A. Einstein

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Offline JimBob

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What happens when the magnetic poles switch?
« Reply #7 on: 24/03/2010 17:21:45 »
http://geomag.usgs.gov/charts/ig00f.pdf

The PDF file linked above will show the total magnetic intensity of the earth as it now exist.

Note that there is no magnetic intensity at the "north pole." In fact there are two areas of maximum intensity, one in Russia, the other just west of Hudson's bay in Canada.

There are also two "south poles" One near the Paraguay-Brazil-Argentina conjunction and another rather close to the present south pole.

This means that the earth's magnetic field is in a state of flux and from what we can see from history, it has always been this way.

I cannot find the "1,000 word essay" I wrote on this several years ago on this site. Oh well. One day the ghosts in the machine will deliver it to the search engines again.
The mind is like a parachute. It works best when open.  -- A. Einstein

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Offline LeeE

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What happens when the magnetic poles switch?
« Reply #8 on: 25/03/2010 16:21:06 »
Hmm... I think it must have been a variation map that I remember seeing, as it's the variation centers that fit with what I recall seeing.  I believe that the 'S' intensity center located over the Paraguay-Brazil-Argentina conjunction is widely known as the SAA (South Atlantic Anomaly) despite being half over land.

Heh! - it's a bit cheeky to include the recycling symbol and "Printed on recycled paper" in a PDF [;)]
...And its claws are as big as cups, and for some reason it's got a tremendous fear of stamps! And Mrs Doyle was telling me it's got magnets on its tail, so if you're made out of metal it can attach itself to you! And instead of a mouth it's got four arses!

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Offline Geezer

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What happens when the magnetic poles switch?
« Reply #9 on: 25/03/2010 17:47:00 »
Haha! JimBob made an Electrical Engineering joke! Nice one JB.


"the earth's magnetic field is in a state of flux"
There ain'ta no sanity clause, and there ain'ta no centrifugal force Šther.

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Offline JimBob

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What happens when the magnetic poles switch?
« Reply #10 on: 26/03/2010 01:17:12 »
Haha! JimBob made an Electrical Engineering joke! Nice one JB.


"the earth's magnetic field is in a state of flux"

(JimBob, musing to himself - "Never thought Geezer was that bright.")
The mind is like a parachute. It works best when open.  -- A. Einstein

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Offline Geezer

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What happens when the magnetic poles switch?
« Reply #11 on: 26/03/2010 04:47:39 »
EE's are always bright on account of the light bulbs that are screwed into their craniums.
There ain'ta no sanity clause, and there ain'ta no centrifugal force Šther.

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Offline Airthumbs

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What happens when the magnetic poles switch?
« Reply #12 on: 08/01/2011 08:08:10 »
Maybe the birds and fish start to die!! 
Any intelligent fool can make things bigger and more complex... It takes a touch of genius - and a lot of courage to move in the opposite direction. (Einstein)