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Reversal of Earth's magnetic field

  1. Apr 28, 2014 #1
    I understand that the sun changes magnetic polarity far more often than Earth does (correct me if I'm wrong as it's just what I read).

    Apparently it is statistically likely that the earth's magnetic field will change polarity at some time, so what sort of effects will this have in practcal terms on us and our environment, apart from ruining the betting odds of any sensible result in pigeon racing or possibly getting the auroras in odd places

    Can you think of any products which would be advantageous to have given this situation if it happened suddenly as I'd like to get in with the patents well before the event!
  2. jcsd
  3. Apr 28, 2014 #2


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    The reversal isn't sudden, it usually happens gradually over a period of 1,000-5,000 years. It's been ~780k years since the last reversal, and scientists say it may happen in another 1,000 years, or not.

    From the many articles and programs I have read, the wikipedia article actually does a fine job of briefly going over the issues.


    I can post other links later. But you should read this first.
    Last edited: Apr 28, 2014
  4. Apr 28, 2014 #3


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    hi Evo,

    you had better correct your 780 million years to 780,000 yrs :wink:

    there's been some 20 - 21 reversals in the last 5 million years

  5. Apr 28, 2014 #4


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    LOL!! Corrected, thanks! I got it correct in other threads I've posted on this. We've had quite a few.
  6. Jul 28, 2015 #5


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    The South Atlantic Anomaly is a dent in Earth's shield against cosmic radiation, 124 miles above the ground (200 kilometers). It may be the most dangerous place in the Earth's sphere for satellites and spacecraft to traverse, because anything electronic traveling through it is vulnerable to strong radiation from space and tends to malfunction.
    Ancient_Huts_May_Reveal_Clues-58374817122448d53b427f4544f04479.jpg [/PLAIN] [Broken]

    particularly hot and dense feature in the mantle below southern Africa and the Atlantic called the Large Low Shear Velocity Province may have something to do with locally weakening the magnetic field and periodic reversals.
    [/PLAIN] [Broken]
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  7. Jul 28, 2015 #6
    What can be the cause of this anomaly?
    Remnant of some ancient collision of the Earth with another protoplanetary body?
    This is not wild speculation. it's pretty much accepted that an event of this kind is the reason why we have a large moon.
  8. Jul 28, 2015 #7


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  9. Aug 4, 2015 #8


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    If the earth spinning core causes the magnetic field then wouldn't it have to be spinning the other direction for the magnetic field to change polarity ? and if the magnetic field is getting weaker does this mean it is going to stop spinning before a reversal? I would be more worried about the atmosphere being blasted into space then getting a patent in.

    You could patent compass paint but I doubt it will make you rich =)
  10. Aug 4, 2015 #9
    I'm not sure of the exact dynamics underlying the generating of Earths magnetic field, I don't think anyone is sure for certain.
    However there is strong evidence of geomagnetic reversal happening previously and several times.
    It's not an event which happens instantly, it can take centuries or millennia to complete, so it probably wouldn't have dramatic consequences on human timescales.
    It's also not very predictable, there having been some reversals which apparently changed back again within quite a short time geologically.
    Last edited: Aug 4, 2015
  11. Aug 7, 2015 #10
    From your link, Rootone:
    I actually happen to know a Geophysics PHD candidate and she assured me this convection model is the most widely accepted at this time. (So accepted that she was surprised when I mentioned there were occasional "uncertainties" about it here at PF.)
    As she explained it to me, there are masses and masses of free electrons in the molten metals of the earth's interior. The molten metal nearest the core is the hottest and it tends to rise as cooler metal from nearer the surface sinks. There results very slow convection currents full of negative charge; she said the motion was on the order of "feet per year." Very slow, but the fact there is such a massive amount of free electrons in it causes it to have a magnetic field.

    At any rate, no geophysicist thinks the core is rotating at some different rate than anything else, or that the core is inert while everything above it rotates. That's a crackpot idea that was proposed in a sci-fi film some years back.
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  12. Aug 8, 2015 #11


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    well tthat makes alot more sense when you put it that way =) thanks
  13. Aug 9, 2015 #12
    There's not much doubt that the generation process is comparable to a dynamo and that convection plays a part.
    What there is doubt about is the reason for anomalies and reversals
  14. Aug 10, 2015 #13
    The Sun changes polarity every eleven years. The mechanism is this: big tubes of magnetic flux form. The tubes have polarity. The negative end of the tube is attracted to the positive pole, and the positive end of the tube to the negative pole. The tubes move slowly, but they get there eventually, weakening the field. Eventually the field reverses polarity.

    The same would happen within the Earth but the iron core resists the reversal. According to a recent simulation, the iron core has opposite polarity than the mantle. The mantle is "trying" to reverse the polarity of the core. Every now and then it succeeds. There is nothing cyclic about it. Knowing the time of previous reversals is no use in predicting the next reversal.

    During the transition the magnetic field does not collapse. Instead the magnetic poles wander over the surface of the Earth. There could be four or more poles instead of the usual two.

    Charged particles are attracted to the poles. These poles could be over cities or whatever, so there could be severe electrical storms in such areas. Such reversals have occurred many times and haven't resulted in mass extinctions, but they would disrupt electronic communications and damage/disable satellites. Power lines would serve as antennae collecting large amounts of energy, causing destructive power surges.
  15. Aug 10, 2015 #14


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    not quite right
    The sunspots change their magnetic polarity every ~ 11 years. The overall magnetic field of the sun changes polarity every 22 years

    The magnetic fields of the sun / sunspots is generated in the Convective Zone. This is the outer zone of the Sun from the surface down to the Radiation Zone. The radiation zone extends from the bottom of the convective zone to the core.
    Unlike the Earth, the magnetic field of the Sun is not generated in the core region

    please provide some references to that .... it sounds a little Sci Fi' ish :wink:

    This already occurs when the Earth's magnet field is subjected to large CME's ( coronal Mass Ejections) from the sun

    Last edited: Aug 10, 2015
  16. Aug 11, 2015 #15
    supercomputer-based simulation of the geodynamo by Gary Glatzmeier of the University of California, Santa Cruz, and his colleagues. "Our solution shows how convection in the fluid outer core is continually trying to reverse the field but that the solid inner core inhibits magnetic reversals because the field in the inner core can only change on the much longer time scale of diffusion." http://es.ucsc.edu/~glatz/geodynamo.html

    Youtube of the results:

    Correct. But there are not all that many power lines or satellites near the Earth's magnetic poles at this time. Should the poles move to populated areas there would be more damage near such poles should a CME occur.
    Last edited: Aug 11, 2015
  17. Aug 16, 2015 #16
    Would these floating poles move the auroras with them?
  18. Aug 16, 2015 #17


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    If the magnetic field was strong enough, the aurora would be present. But if the migrating pole was weak, the aurora would not be as distinct.
  19. Aug 16, 2015 #18
    If all the poles are scattered it may not even be strong enough to illuminate then...
  20. Aug 20, 2015 #19
    The assumption that a geomagnetic field reversal takes 2000 to 5000 years has been proven to be incorrect by paleo geomagnetic analysis.

    In the last 10 years it has been found that the geomagnetic field changes rapidly and cyclically.

    What drives that change is not known.


    "Is the geodynamo process intrinsically unstable?

    Recent palaeomagnetic studies suggest that excursions of the geomagnetic field, during which the intensity drops suddenly by a factor of 5 to 10 and the local direction changes dramatically, are more common than previously expected. The `normal' state of the geomagnetic field, dominated by an axial dipole, seems to be interrupted every 30,000 to 100,000 kyr; it may not therefore be as stable as we thought.

    Recent studies suggest that the Earth's magnetic field has fallen dramatically in magnitude and changed direction repeatedly since the last reversal 700 kyr ago (Langereis et al. 1997; Lund et al. 1998). These important results paint a rather different picture of the long-term behaviour of the field from the conventional one of a steady dipole reversing at random intervals: instead, the field appears to spend up to 20 per cent of its time in a weak, non-dipole state (Lund et al. 1998). One of us (Gubbins 1999) has suggested that this is evidence of a rapid natural timescale (500 yr) in the outer core, and that the magnetic field is usually prevented from reversing completely by the longer diffusion time of the inner core (2 to 5 kyr). This raises a number of important but difficult questions for geodynamo theory. How can the geomagnetic field change so rapidly and dramatically? Can slight variations of the geomagnetic field affect the dynamics of core convection significantly? If so, is the geodynamo process intrinsically unstable?"


    "New evidence for extraordinary rapid change of geomagnetic field during a reversal

    Palaeomagnetic results from lava flows recording a geomagnetic polarity reversal at Steens Mountain, Oregon suggest the occurrence of brief episodes of astonishingly rapid field change of six degrees per day. The evidence is large, systematic variations in the direction of remanent magnetization as a function of the temperature of thermal demagnetization and of vertical position within a single flow, which are most simply explained by the hypothesis that the field was changing direction as the flow cooled."


    "The tectonic and geomagnetic significance of paleomagnetic observations from volcanic rocks from central Afar, Africa

    Reheating and partial remagnetization by the overlying flow cannot explain either of the transitional directions because both differ significantly from that of the reversely magnetized overlying flow. The high-temperature component gives a VGP in the northern Pacific, whereas the lower-temperature component gives a nearly antipodal VGP south of Cape Town, South Africa. Hence, the configuration of the geomagnetic field appears to have jumped nearly instantaneously from a northern-hemisphere transitional state to a southern-hemisphere one during this normal to reverse polarity transition."
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  21. Aug 20, 2015 #20
    The European set of three satellites SWARM is now providing almost real time global analysis of the geomagnetic field with laboratory like precision.

    It has found that the geomagnetic is currently dropping at 5%/decade which is 10 times faster than is possible based on the current assumed model of the geomagnetic field.



    "Earth's Magnetic Field Is Weakening 10 Times Faster Now
    ...Previously, researchers estimated the field was weakening about 5 percent per century, but the new data revealed the field is actually weakening at 5 percent per decade, or 10 times faster than thought. (Betzalel: 10 times faster than physically possible if the cause of the geomagnetic field changes is changes at the liquid core/solid core boundary) As such, rather than the full flip occurring in about 2,000 years, as was predicted, the new data suggest it could happen sooner.
    Floberghagen hopes that more data from Swarm will shed light on why the field is weakening faster now."

    One of the reasons the SWARM satellites were designed was to try to understand the reasons for the sudden acceleration of the North Magnetic Pole drift.


    "What Caused Recent Acceleration of the North Magnetic Pole Drift?

    The north magnetic pole (NMP) is the point at the Earth’s surface where the geomagnetic field is directed vertically downward. It drifts in time as a result of core convection, which sustains the Earth’s main magnetic field through the geodynamo process. During the 1990s the NMP drift speed suddenly increased from 15 kilometers per year at the start of the decade to 55 kilometers per year by the decade’s end. This acceleration was all the more surprising given that the NMP drift speed had remained less than 15 kilometers per year over the previous 150 years of observation. Why did NMP drift accelerate in the 1990s?

    Answering this question may require revising a long-held assumption about processes in the core at the origin of fluctuations in the intensity and direction of the Earth’s magnetic field on decadal to secular time scales, and hints at the existence of a hidden plume rising within the core under the Arctic."
  22. Aug 20, 2015 #21
    The following is an interesting PBS Nova documentary that explains the analysis methods (Study of ancient fired pottery such as floor tiles in ancient buildings The floor tiles are dated and the manufacturer is marked on the tile. The scientists are therefore able to trace the ancient floor tile to a specific kiln - interesting detective work - the fired pottery freezes the magnetic orientation and field strength when the pottery cools.) which has used to discover that the geomagnetic field orientation changes abruptly (10 to 15 degrees) in reference to the rotational axis of the planet and the geomagnetic field strength also changes abruptly and cyclically.

    As noted the discovery that the geomagnetic field changes abruptly and cyclically was not expected and creates a paradox for the core based model.


    Cyclic Archeomagnetic Jerks
    The newly discovered (over the 15 years) short term cyclic (cycles 400 years and 1400 years) abrupt geomagnetic field changes are called archeomagnetic jerks as they were found by analyzing pottery. The labeling of the phenomena as an 'archeomagnetic jerk' is unfortunate as most non-specialists confuse the very, very large archeomagnetic jerks (which are an observational breakthrough, something new and exciting, as they have no theoretical explanation and are a paradox) with the very small geomagnetic jerks which can be explained by the core based model.

    Cyclic Geomagnetic Excursions
    The second finding is that are cyclic geomagnetic excursions. During a geomagnetic field excursion the geomagnetic field intensity drops by a factor of 5 to 10 (Cycles of 30,000 years and 100,000 years).

    The observational finding (over the last 15 years) that the geomagnetic field changes abruptly and cyclically (archeomagnetic jerks and geomagnetic excursions) was not expected, as it is assumed the geomagnetic field and/or geomagnetic field changes are 100% caused by internal thermal convection type movement of magma in the core of the earth.

    There is no known mechanism that can suddenly cause internal thermal convection in the earth's liquid core to change rapidly and to change cyclically. Also there is a back emf generated in the conductive liquid core which strongly resists any rapid changes to the geomagnetic field.
  23. Aug 22, 2015 #22
    This PBS NOVA documentary is interesting and pertinent to the subject of this thread. The NOVA documentary includes interviews of some of the key geomagnetic specialists that have been involved in the formulation of the current geomagnetic field theory (Including Gubbins and the author of the Stern paper. See the link to the papers above and the NOVA documentary.)


    The geomagnetic specialists note in the documentary that it appears possible based on the fact that the North pole drift velocity increased by a factor of ten, from 15 km/yr to 55 km/yr starting in the mid 1990s (the abrupt change to north magnetic pole drift velocity was discussed in a previous NOVA documentary which also discussed the discovery of archeomagnetic jerks - sudden changes in the tilt of the geomagnetic field of 10 to 15 degrees - by analyzing ancient fired floor tiles) and the geomagnetic field intensity drop has increased by a factor of ten from a drop of 5% per century which it had been dropping at for the last 200 years or so, to a drop of 5% per decade (this is the finding of the European SWARM satellite analysis which shows that the drop in geomagnetic intensity is over a large region of the earth, concentrated over the North and South America continents) also starting sometime in the 1990's that a geomagnetic excursion appears to be starting which may lead to a geomagnetic reversal.

    As noted in the papers quoted above and in this comment, there is evidence of some large unknown forcing function that causes cyclic geomagnetic field changes and which correlate with cyclic climate change and that for the larger forcing events correlate with sudden anomalous volcanic activity.

    What caused the past cyclic abrupt changes to the geomagnetic field is possibly what changed in the mid 1990's to cause the sudden abrupt change to the geomagnetic field that is causing the north magnetic drift velocity change and the sudden drop in the geomagnetic field strength.

    Earth based forcing functions are expected to be chaotic and hence are not expected to be periodic. There are no earth based mechanisms that are capable of causing a sudden and rapid cyclic change of convection flow in the earth's core or a cyclic change to the earth's geomagnetic field or the earth's climate.

    The authors of this paper note it is anomalous that five volcanoes that have separate magma chambers all erupt within a 100 year period. The authors fail to note that it is also anomalous that there is a geomagnetic excursion (which is a rare and unusual event) that is going on at the same time that this anomalous eruption of five unconnected volcanoes is occurring. i.e. It is logical to ask if there is connection between the two events and hence what could cause both events to occur at the same time.

    Simultaneous Volcanic Eruption Paradox which correlates with a geomagnetic excursion.

    Geomagnetic excursion captured by multiple volcanoes in a monogenetic field
    Five monogenetic volcanoes within the Quaternary Auckland volcanic field are shown to have recorded a virtually identical but anomalous paleomagnetic direction (mean inclination and declination of 61.7° and 351.0°, respectively), consistent with the capture of a geomagnetic excursion. Based on documented rates of change of paleomagnetic field direction during excursions this implies that the volcanoes may have all formed within a period of only 50–100 years or less. These temporally linked volcanoes are widespread throughout the field and appear not to be structurally related. However, the general paradigm for the reawakening of monogenetic fields is that only a single new volcano or group of closely spaced vents is created, typically at intervals of several hundred years or more. Therefore, the results presented show that for any monogenetic field the impact of renewed eruptive activity may be significantly under-estimated, especially for potentially affected population centres and the siting of sensitive facilities.

    In the late 1990's it was discovered that there is cyclic abrupt climate change based on the analysis of the Greenland ice sheet core. The abrupt climate change events (Heinrich events roughly every 8000 to 10,000 years. The Heinrich events fall on the same series as the 1470 year events which indicates they may have the same forcing function.) correlate with geomagnetic excursion like changes to the geomagnetic field. The lesser climate change event the Dansgaard-Oeschger events (1470 years) correlate with archeomagnetic jerks.

    "Also, we wish to recall that evidence of a correlation between archeomagnetic jerks and cooling events (in a region extending from the eastern North Atlantic to the Middle East) now covers a period of 5 millenia and involves 10 events (see f.i. Figure 1 of Gallet and Genevey, 2007). The climatic record uses a combination of results from Bond et al (2001), history of Swiss glaciers (Holzhauser et al, 2005) and historical accounts reviewed by Le Roy Ladurie (2004). Recent high-resolution paleomagnetic records (e.g. Snowball and Sandgren, 2004; St-Onge et al., 2003) and global geomagnetic field modeling (Korte and Constable, 2006) support the idea that part of the centennial-scale fluctuations in 14C production may have been influenced by previously unmodeled rapid dipole field variations. In any case, the relationship between climate, the Sun and the geomagnetic field could be more complex than previously imagined. And the previous points allow the possibility for some connection between the geomagnetic field and climate over these time scales."

    Timing of abrupt climate change: A precise clock by Stefan Rahmstorf
    Many paleoclimatic data reveal a _1,500 year cyclicity of unknown origin. A crucial question is how stable and regular this cycle is. An analysis of the GISP2 ice core record from Greenland reveals that abrupt climate events appear to be paced by a 1,470-year cycle with a period that is probably stable to within a few percent; with 95% confidence the period is maintained to better than 12% over at least 23 cycles. This highly precise clock points to an origin outside the Earth system; oscillatory modes within the Earth system can be expected to be far more irregular in period."

    There have been an interesting set of new papers and research findings concerning the sun including the below linked paper and concerning what is currently happening to the sun which are interesting and may possibly provide an explanation as to past changes to the geomagnetic field what is currently happening to the geomagnetic field. I will start a new thread in astrophysics to present the papers.


    The peculiar solar cycle 24 – where do we stand?
    Last edited: Aug 22, 2015
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