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Why do the Earth's magnetic poles switch every once in a while?

  1. Apr 8, 2009 #1
    My geology prof says that no one knows.

    I think I'll cry if that's true.

    It's driving me nuts.
  2. jcsd
  3. Apr 9, 2009 #2
    No one knows. Which is not to say that there's anything new or exciting about this phenomenon (although there may be). It's simply a reflection of the fact that it's rather difficult to get precise data and build models of stuff going on in the interior of the earth (it being rather huge and inaccessible). It seems reasonable to me that small effects in magnetofluid dynamics would cause a magnetic dipole which fluctuated chaotically (chaos as in chaos theory, not the layman meaning of the word) and thus non-periodically, as for the specific starting conditions and which small effects have dominance in the earth's center... well we can't exactly just go and check. That being said I know very little about magnetofluid dynamics so maybe there's an astro person on here who could answer the question better.
  4. Apr 9, 2009 #3
    Your geology proof is wrong.
    Have not you heard about "Chandler wobble"? The poles on the Earth have changed places - many times! We can tell this has happened because the magnetic moment of the rocks that make up the ocean floor have an alternating direction. Which direction they exhibit depends on which way the poles were oriented when the rocks were being formed at the mid-ocean ridge.
    During a reversal, which can take thousands of years, the magnetic poles start to wander away from the region around the spin poles, and eventually end up switched around.

    The location of the North geographic pole wanders in a small erratic circle-like path, called the "Chandler wobble." This motion is less than 6 meters per year on the surface

    Sometimes this wandering is slow and steady, and other times it occurs in several jumps. One of the things that does consistently happen during a reversal is that the strength of the magnetic field decreases to almost zero.
    The poles are not far more restless. The magnetic poles are far more restless. They move under the influence of the dynamo currents in the Earth's core, as well as electric currents flowing in the ionosphere. The North magnetic pole seems to be moving northward at an average rate of 10 kilometers per year. Yet there is also some elliptical motion .
    You can check out this site for further info
    http://en.wikipedia.org/wiki/Magnetic_polarity_reversal" [Broken]
    Last edited by a moderator: May 4, 2017
  5. Apr 9, 2009 #4
    What you've provided aaryan0077 is a PHENOMOLOGICAL DESCRIPTION not an explanation. Noting that there is a wobble is not understanding, accurately PREDICTING where the earth's magnetic pole is going to be in the next second,minute, millenia and understanding WHY it behaves this way is understanding (and I mean why in a quantifiable, exact, experimentally provable way, not in a 'well, like, the earth's got charge in it, and like, it's a fluid, that's why it happens' sort of way).

    As I said before, our lack of an accurate mathematical model is really just due to the size of the system and the difficulty of getting accurate data and at the end of the day, it's going to be a chaotic system (like the weather), which is to say, unless we know the EXACT position and momentum (ignoring quantum effects) of every single particle in the system and could solve the coupled differential equations of their motion (for a bench mark, if every atom on the planet was actually a bit in a modern computer we could do this for maybe 13 electrons without making approximations) the error in our initial conditions and the error from the approximations made in our model will cause us to lose all accuracy after a short amount of time. So, like the weather, there's not really anything new or interesting happening (the physics is pretty basic) but the enormity of the system and the sensitivity of the solutions to initial conditions means we'll never be able to predict the weather (unless we have a computer the size of our galaxy at our disposal) with complete accuracy.
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