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Thread: Earth magnetic pole flips

  1. #1
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    Earth magnetic pole flips

    Simple question but I doubt if there is one single simple answer:

    Could the Earth's magnetic field be reversed by a large (=massive) solar CME? ie. could the attendant magnetic flux re-magnetise the Earth?

    I'm curious because current theory indicates that the Eart's magnetic field does reverse periodically but is thought to do so over a few millenea, not virtually overnight.

  2. #2
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    If the following assumptions, which are pretty good,

    Assumption 1.) The particles are moving directly away from the sun in the ecliptic when they hit the Earth.

    Assumption 2.) The magnetic field goes from north to south, which is (more or less) perpendicular to the ecliptic.

    This means that the torque induced on the Earth's iron core which will tend to resist the geodynamo's rotation. This assumes I've done my "right hand rules" correctly, the odds of this are about 50-50.

    Now will this have any noticible effect? I don't know how "charged" a CME is. If you know this, you can calculate the F ( = -q(v X B)). From this one calculates the torque on the core, and the resulting angular acceleration. And the required duration of the CME to change the rotation of the core.

    It's getting late and I'm too lazy to do the calculations. So I'll let someone else have at it. :wink:

  3. #3
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    Could a CME flip the earth's magnetic field? I can give you a definite maybe on that one.

    Could the earth's magnetic field flip? Of course it could -- it's done it all by itself numerous times in the Earth's geohistory. The 'polarity reversal' history of the magnetic field is preserved in layers of rock in volcanic areas. The magnetic field causes a particular orientation of magnetic particles in lava, and that orientation is frozen when the lava solidifies. Succeeding layers show flipflops back and forth over the millenia.

    Will the earth's magnetic field flip again? Yes.
    Will it happen any time soon? There is evidence it's happening now. It's an extremely slow process, taking many thousands of years to complete. Some say the current drift of the Magnetic North Pole calculated at 40km per year is a symptom of the eventual field collapse/reversal.

    When this reversal happens, will the planet literally flip over? Nancy&Co notwithstanding, no. The Earth will not physically move. The only thing that will change when it's all over will be which end of the compass needle points toward the "N".

    Do we need to worry? Not about this...

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    Your odds on the right hand rule are 50-50? Alot better than mine...

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    Quote Originally Posted by Wiley
    Assumption 1.) The particles are moving directly away from the sun in the ecliptic when they hit the Earth.

    Assumption 2.) The magnetic field goes from north to south, which is (more or less) perpendicular to the ecliptic.

    This means that the torque induced on the Earth's iron core which will tend to resist the geodynamo's rotation. This assumes I've done my "right hand rules" correctly, the odds of this are about 50-50.
    I've told this story before.

    A well-respected geology professor of mine once tried to explain the magnetic field to a class of geology students, and ended up making three huge blunders--all of which cancelled each other and made it look like he was right.

    He said the Earth spinning causes a rotating current. Use the right hand rule, and you notice that your thumb points north. QED.

    When you use the right hand rule, your hands are curled in the direction of the current flow--if an electron were on the equator, the current flow would be opposite the direction of the rotation, since by convention current flow is postive to negative. So, your thumb would point south.

    But, the North Pole of the Earth is actually a south-magnetic pole--because that's where the north poles point, as opposites attract. So, his logic would still work, if you ignore that the Earth's magnetic field doesn't line up with the rotation axis, and it rotates with the planet.

  6. #6
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    The sun's magnetic field flips every 11 years, completing a 22 cycle where it returns to its original position. The sun doesn't flip over and the sun doesn't change spin direction. It's generally thought that the sun's magnetic field is a surface phenomena. And indeed, the surface of the sun gets a lot of sunspots when the magnetic field goes through zero every 11 years of this cycle.
    I've asked the question as to whether the sun's magnetic field cycle could be caused by an outside force or wave going through the galaxy and making it change. The answer is truly not known. But it certainly seems that other stars also have a sunspot cycle and their cycle is not the same 22 year cycle as the sun's.
    So the earth's magneic field is thought not to be a result of really big bar magnet, but rather a "surface" effect on the outside of the earth's core like the sun's. When the earth's magnetic field flips it acts like the sun's flip. Whether this is caused by an external force such as big CME's or other effects or whether it is internally generated is really not known to me.

    Do we have to worry about the effects of a magnetic field flip of the earth? Probably YES. It may well allow a lot more ionizing radiation to hit us when the field strength goes through zero. I personally would spend more time indoors.

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    The toatl field does not drop to zero, only the dipole component. There are still quadropole and higher components. So, while compasses will be useless, the defences against ionizing radiation will not be completely down.

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    Quote Originally Posted by John Kierein
    The sun's magnetic field flips every 11 years, completing a 22 cycle where it returns to its original position. The sun doesn't flip over and the sun doesn't change spin direction. It's generally thought that the sun's magnetic field is a surface phenomena. And indeed, the surface of the sun gets a lot of sunspots when the magnetic field goes through zero every 11 years of this cycle.
    Right.
    Quote Originally Posted by John Kierein
    So the earth's magneic field is thought not to be a result of really big bar magnet, but rather a "surface" effect on the outside of the earth's core like the sun's.
    Is this your personal speculation? From the discussion provided below, this would appear to be wrong.
    Quote Originally Posted by John Kierein
    Do we have to worry about the effects of a magnetic field flip of the earth? Probably YES. It may well allow a lot more ionizing radiation to hit us when the field strength goes through zero. I personally would spend more time indoors.
    This is definitely wrong. See the discussion below, provided from this site.
    Earth’s magnetic field also flips, but with less regularity. Consecutive reversals are spaced 5 thousand years to 50 million years apart. The last reversal happened 740,000 years ago. Some researchers think our planet is overdue for another one, but nobody knows exactly when the next reversal might occur.

    Although solar and terrestrial magnetic fields behave differently, they do have something in common: their shape. During solar minimum the Sun's field, like Earth's, resembles that of an iron bar magnet, with great closed loops near the equator and open field lines near the poles. Scientists call such a field a "dipole." The Sun's dipolar field is about as strong as a refrigerator magnet, or 50 gauss (a unit of magnetic intensity). Earth's magnetic field is 100 times weaker.

    RADIATION FROM THE SUN: Sunlight of course is undisturbed. High-energy protons from the Sun are usually diverted by the magnetic field. During the reversal the field probably does not disappear, but becomes complex and weaker, and protons can more easily reach the atmosphere, as they do now within 1000 miles or so of the magnetic pole. On the ground it makes no difference because the thick atmosphere shields us very well, and none of the protons penetrates far into it.

    Some people worry that during magnetic reversals the Earth would receive a higher dosage of high-energy ions and electrons ("radiation" in common terms), which might affect us and any living creatures on Earth. This is not so. Even today, the magnetic shield is not effective near the magnetic poles, yet the radiation received there on the ground is only slightly higher than anywhere else. The reason is that our main shield against such particles is not the magnetic field of the Earth but the atmosphere, equivalent to some 10 feet of concrete.

    In any case, during reversal the magnetic field does not go away, it only gets weaker and develops several more magnetic poles, at unpredictable locations.

    The change, whenever it occurs, will be gradual and the field will not drop to zero in between--doing so would mean that the magnetic energy of the Earth was somehow converted or dissipated, and all processes we know for this tend to run on scales of thousands of year, if not more. Right now the main (dipole) field is getting weaker at a rate of about 7% per century, and if you draw a straight line through the points you find it reversing between 1000 and 2000 years from now. It might happen, although the trend may well change. The energy of the field, however, has hardly changed. What seems to have happened is that the more complicated parts of the field (equivalent to several magnets in different directions) have got stronger while the main two-pole ("dipole") field lost strength. The complex field is somewhat weaker (it drops off faster with distance from the source, which is the core of the Earth), but we should not expect the field to be ever greatly weakened.

    The polar field of the Sun seems to reverse every 11 years or so, taking about a year or more. But the Sun's magnetism is different, it has foci right on the surface, in sunspots.
    Everyone is entitled to his own opinion, but not his own facts.

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    The sun's is on the surface. Mars' is on the surface. The earth's is generally thought to be on the surface of the the core, and also not a true bar magnet. The core itself is probably too hot to retain manetism. (you can destroy the magnetism of an iron bar magnet by heating it.)

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    Thanks for all the input guys!

    It is rather neat the way the Earth has left a recording of magnetic data in parallel bands either side of deep ocean trenches as the Earth's tectonic plates move apart and fresh magma rises to cool and form new sea bed. Almost analogous to tree rings being used to determime past weather patterns. It is precisely this that had set me thinking. From the records it shows how conditions change over long periods of time but a tree ring wouldn't show the effects of a severe local thunderstom (unless the tree got a direct hit!) but it does record the effects of a cold summer or a warmer than usual winter.

    As I understand it, the Earth's field is more a deep earth phenomenum (magma flows under the mantle could somehow act like a ponderous jetstream and produce the toroidal fields if sufficient current flows though them). It wouldn't explain the N/S orientation of the mid atlantic trench though so a totaly different mechanisim would have to be at work there. My own feeling (with no specialist knowlwdge) is that plate tectonics and the Earth's field are both driven by the same forces, possibly nuclear decay, heat causing deep currents below the semi-plastic mantle. The N/S trench is a puzzle though, I would have expected it to be equatorial.

    Am I worried about a possible reversal caused by a CME?

    Yes and no!

    My life would become totaly disrupted: like John Kierein, I would spend much of my daylight hours indoors (asleep!) so I could spend the whole night watching the fantastic aroras that would be produced! Then there is also the rule that dictates cloud cover in Scotland is directly proportional to the square of the index of astronomical activity.

    Worry, worry, worry!!!

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    Quote Originally Posted by frogesque
    As I understand it, the Earth's field is more a deep earth phenomenum (magma flows under the mantle could somehow act like a ponderous jetstream and produce the toroidal fields if sufficient current flows though them). It wouldn't explain the N/S orientation of the mid atlantic trench though so a totaly different mechanisim would have to be at work there. My own feeling (with no specialist knowlwdge) is that plate tectonics and the Earth's field are both driven by the same forces, possibly nuclear decay, heat causing deep currents below the semi-plastic mantle. The N/S trench is a puzzle though, I would have expected it to be equatorial.
    It's the mid-atlantic ridge not trench, and there are many other ridges and trenches around the world.

    But I'm curious why you would expect an east-west ridge rather than a north-south ridge? How do you imagine the flow?

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    milli360 wrote:

    "It's the mid-atlantic ridge not trench, and there are many other ridges and trenches around the world.

    But I'm curious why you would expect an east-west ridge rather than a north-south ridge? How do you imagine the flow?"


    Don't know my trenches from my ridges thanks for the correction. The ridges are highest at the separation and gradually drop in height until they disappear beneath the continental shelves. The mid Atlantic ridge is I believe the largest of these.

    An east west orientation would be logical if fluid flow is similar to a jet stream - look at cloud formations on Jupiter, Neptune or even Earth.

    However, thinking some more, if circulation of these (presumed) thermal currents were contained between a semi-solid pack of tectonic land sheets at the outer surface and a solid internal core then net fluid flow could be in a N/S direction. If it also had a rolling motion like an airplane tip vortex then there could possibly be a region orientated likewise where the vorticies run together in opposite rotation to produce an upwelling motion - hence the ridge and separation of the two ajoining plates. Obviously, this fluid has to go somewhere and could be sinking at the poles to be reheated and re-cycled. I don't imagine this to be a sedate motion on a long time scale - more of a boiling turbulent motion with upwellings and downward cool spots producing secondary vortices elswhere. Could that type of movement create a north pole / south pole toroidal magnet with a propensity to move around relative to the Earth's axis of rotation?

    I really don't know and am just kind of thinking aloud. It also has to be remembered that we would be dealing with an odd type of fluid, semi-plastic at the top junction with "normal" magma underneath the plates and more highly mobile at greater depth untill it meets the core boundary layer. It would also be under intense pressure and so hot it would probably vaporise in normal atmosphere. Hardly an "ideal" fluid!

    Sorry for the long post - that's the problem when you start thinking!

  13. #13
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    Quote Originally Posted by frogesque
    An east west orientation would be logical if fluid flow is similar to a jet stream - look at cloud formations on Jupiter, Neptune or even Earth.

    However, thinking some more, if circulation of these (presumed) thermal currents were contained between a semi-solid pack of tectonic land sheets at the outer surface and a solid internal core then net fluid flow could be in a N/S direction. If it also had a rolling motion like an airplane tip vortex then there could possibly be a region orientated likewise where the vorticies run together in opposite rotation to produce an upwelling motion - hence the ridge and separation of the two ajoining plates. Obviously, this fluid has to go somewhere and could be sinking at the poles to be reheated and re-cycled. I don't imagine this to be a sedate motion on a long time scale - more of a boiling turbulent motion with upwellings and downward cool spots producing secondary vortices elswhere. Could that type of movement create a north pole / south pole toroidal magnet with a propensity to move around relative to the Earth's axis of rotation?
    I would agree that fluid flow in the mantle would be more likely (intuitively) East/West, but what makes you think trenches and/or ridges should be oriented in a parallel direction because of this? If anything, I'd think the trenches/ridges ought to be perpendicular to flow, since they'd be pulling apart/pushing together in the E/W directions. If you push the ends of a piece of paper toward each other, do you get a hump/dip in the paper lengthwise, or across the paper?

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    The core of the earth is thought to be spinning faster than the surface, so the flow may be west/east?? But I doubt it slows down during a magnetic field reversal or has much of anything to do with it.

  15. #15
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    Just a few notes. Field data are also recorded in some pottery - quite a well detailed record considering the established dating of such artifacts. Anyone interested in field reversals should visit this link.

    There is a wealth of evidence which suggests the field is undergoing changes at the present time. Anyone who has seen footage of mission control will recall the letters 'SSA' shown on the map which displays the orbital tracks for the ISS and so on. SSA stands for South Atlantic Anomaly - this is an area where the field is weaker; some recent research seems to indicate that these areas (the SSA is not unique) are the first steps in a reversal process. In practical terms, this anomaly allows charged particles/radiation to penetrate more deeply, potentially harming any orbital electronics and of course organic material.

    During a reversal, this kind of effect can be expected globally. While it is true the atmosphere provides the lion's share of our protection, we ourselves on the surface are not the only concern. While all life on earth would not end if all satellites and such that could be effected by a reversal were indeed damaged or incapacitated, the realities of our reliance upon them mean there would be significant consequences. I'll take it as a given that there are details as regards just what hardware is at what orbital altitude which one must consider when assessing risk, and that the impact of that scenario depends largely on those facts.

    Additionally, depending on the length of time during which the field is weak (one reversal was quite fast, with the pole moving about 6 degrees per day) - or non-existent - the atmosphere itself is vulnerable. One must also remember that the earth is not in a vacuum. There are a number of realities which are or could be part of a reversal event and it's practical effects on life on earth:

    -The 'character' of the reversal: it's duration from start to flip, the duration of the field absence, if any, the severity and location of any pre-cursor anomalies and so on
    -The health of our atmosphere (ozone holes, etc.)
    -The existence, timing and effect of any solar events/CME's and their attributes: even with a full strength field, effects can be significant depending on the relative orientation of the impacting particle stream.
    -The timing of either of the two above events in relation to our position in the galactic environment and any resulting effects.*
    -Any untimely cosmic events that would otherwise have negligible effects.

    I just want to elaborate a bit on the 4th point. Originally I started doing so in this post, but it was a bit too long, so I've put it here. The main point of the above list is that while it is unlikely anything disasterous will happen due to the natural dynamics of our field and it's flipping, in a worst case scenario, the potential for disaster does indeed exist. While I wouldn't suggest we base action on worst case scenarios (although in other areas of human endeavour, some of them trivial in a relative sense, that is the standard practice), I do think it is important to be aware of them. And in terms of discussion of this particular topic, it is worth mentioning.

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    Quote Originally Posted by Anthrage
    There is a wealth of evidence which suggests the field is undergoing changes at the present time. Anyone who has seen footage of mission control will recall the letters 'SSA' shown on the map which displays the orbital tracks for the ISS and so on. SSA stands for South Atlantic Anomaly - this is an area where the field is weaker; some recent research seems to indicate that these areas (the SSA is not unique) are the first steps in a reversal process. In practical terms, this anomaly allows charged particles/radiation to penetrate more deeply, potentially harming any orbital electronics and of course organic material.
    [nitpick]
    I believe that would be the 'SAA' to which you refer.
    [/nitpick]
    (Farewell, Bad Fellow-ness!)

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    Yep, that's what happens when you write a post with SAA and ISS in the same sentence at 7am after being up all night.

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    We may not get hit by enough protons to cause us any damage when the pole strength weakens but what about the hundreds of satellites orbiting the Earth? Does the present mag feild protect them in any way? Imagine telecommunications going back to the level of the 1960's.

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    Yikes. Cosmic dust increases! This dust has mites in it that cause diseases on earth. Black cloud!

    http://www.geocities.com/CapeCanaveral/Galaxy/7827/

    Drag from the dust will cause us to spiral into the sun! It will cause asteroids to spiral in to earth's orbit and hit us! Has anybody told the Weekly World News about this?

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    Question: What if there were unusually huge number of Sun spots, can this dim the Sun considerably? Would this be an indicator that a massive CME will be imminent? Would this compress the Earth's magnetic field so much that for a period of time, the magnetic field disappears and scorching people on Earth?

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