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Planet magnetic field

  1. Jun 21, 2005 #1
    any body can explain why the circulation of the molten core inside a planet can produce magnetic field?
  2. jcsd
  3. Jun 22, 2005 #2
    If you know that moving charges result in currents , this currents produce a magnetic field around them in the form of closed loops.Similarily molten core inside a planet can be thought of consisting of molten-metals and moving charges.

    Although there has been no avid proof.But planet's magnetic field can be thought of due to circulating currents induced in molten liquid and conducting materials present inside the core.The charges circulate due to eart's rotation around its own axis.
  4. Jun 22, 2005 #3
    Yes I understand it. What wonders me is I always think the molten larva is electrically neutral, so the + and - charges are rotating in the same direction resulting in counteracting magnetic field, so canceled out each other.

    Unless the molten larva is not electrically neutral, then what we have is similar to permanent magnet. no problem.

    What makes the molten larva have excess charge? (or is it?)

    thank you.
  5. Jun 22, 2005 #4


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    There are no molten larvae at the centre of the Earth. (Now THOSE would be some serious Killer Bees!) 'Lava' on the other hand... ;) *

    The core is constantly moving and charges are moving all the time. Electrons build up in places and are drawn from others. While the core as a whole may be electrically neutral, localized parts of it (even very large localized parts) will get charged.

    Think of a thunderstorm. The movement of air masses causes imbalances of charge all through large masses of clouds.

    (* P.S. Actually, there isn't any lava at the centre of the Earth either. Molten rock is only called lava when it reaches the surface.)
    Last edited: Jun 22, 2005
  6. Jun 22, 2005 #5


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    Hey, and I thought I was the only one who used this expression!
  7. Jun 22, 2005 #6
    excuse my english. yup,... i mean lava.

    it is actually magma.

    magma . . . lava . . . larva . . .larvae . . . . :tongue2:

    ok ... ok ...
  8. Jun 24, 2005 #7


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    But we're not talking about local magnetic fields, are we ?

    To the OP : Look up the Dynamo Effect. It's the best explanation out there right now, but the question of the origin of terrestrial fields is far from well-answered.
  9. Jun 27, 2005 #8
    No lava, no magma, just a liquid outer core that it thought to be mainly consisting of iron, the inner core being solid again. Which means that it is conductive, which means that the moving around of charged particles like in a thunderstorm doesn't hold up. Air does not conduct electricity. Which means that the molten core must have an electrical charge for the dynamo effect.

    Perhaps that this charge is caused by boundary effects with the mantle?

    Finally, the flows of the liquid outer core are most likely not caused by the Earth rotation but by heat convection. Otherwise polarity reversals would not be possible.
  10. Jul 1, 2005 #9
    hehe sorry but that was funny!
  11. Jul 3, 2005 #10


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    That it was. As I was reading through the posts, I realized that the 'larva' thing needed to be pounced upon, but wasn't sure how to do it without making it sound like an insult. Well, done, Dave. :approve:
  12. Jul 7, 2005 #11
    It is my understanding that the magnetic field of the earth switches polarity, or at least there is evidence that has shown this sort of event to have occurred before. My question then is, if the polarity is changing is there a time when the earth has NO magnetic field since it must cross the zero point in order to swith polarity. What might the consequences from this be?
  13. Jul 20, 2005 #12
    Cosequences of polarity reversals?

    The usual stuff; nothing serious...
    whales beaching themselves;...

    normally expert sailors becoming lost for weeks at sea;....
    airplane pilots leaving Chicago heading for Florida ending up on Canadan radar;

    African killer bees head for America;.... :bugeye:

    Parents of Boy Scouts on a hiking trip in the Smokies call in the Coast Guard to rescue their kids from the Grand Canyon.... :biggrin:

    Eddie Bauer & Discover Stores, Inc. are forced to recall 50 million defective compasses with faulty N and S labels, as their stock prices plummet 90% due to massive lawsuits for damages due to injurous navigation.

    10 billion birds that usually fly South for the winter fly North, freezing to death on the polar ice caps. :yuck:

    55,000 geologists & geophysicists apply for part of the $1 billion US grant money to study the problem and make recommendations to Congress on how to re- reverse the earth's polarity. :biggrin:
    Last edited: Jul 20, 2005
  14. Jul 21, 2005 #13
    From my knowledge it is not necessary to have plus or minus charges to have a magnetic field, more so the actual movement of the body creates the magnetic field.
  15. Jul 21, 2005 #14


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    Please explain how this is possible.
  16. Jul 21, 2005 #15
    Just to let you know before you brutally cut me down, all I am trying to do is learn. In my view it seems that the magnetic field is caused by the slowing down of time around the particle and not so much the forces at work in the exchange of photons and movement of these. Does, theoretically, a nonmoving charged particle still have a magnetic field.
  17. Jul 21, 2005 #16


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    Then you are trying to propose something very vaguely that contradicts conventional EM theory. Are you aware of this? And are you aware of PF's guildelines regarding such things when you explictly agreed to them when you signed on?

  18. Jul 21, 2005 #17

    Tom Mattson

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    While it is true that an electrically neutral body can have a nonzero magnetic field, it is equally true that the magnetic field would not exist if it were not for the electric charges on the constituent particles. Also, no movement is necessary, thanks to quantum mechanical spin. A stationary charged particle with spin is a magnetic dipole.

    Well then you've come to the right place, because PF is GREAT for that...

    ...but unfortunately this isn't the way to go about it. There are lots of professionals and grad students here who can answer your questions, and they'll be happy to do it. What we frown upon here is unfounded speculation. OK?

    Yes. See my answer regarding spin above.
    Last edited: Jul 21, 2005
  19. Jul 21, 2005 #18
    I'm not sure if you answered my question the way I was asking it Creator. But let me just ask it again.

    If the polarity is changing is there a time when the earth has NO magnetic field since it must cross the zero point in order to swith polarity. What might the consequences from this be?
  20. Jul 21, 2005 #19


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    Start with a global communications blackout. There's also the possible extermination of most life. We live in a veritable maelstrom of energetic particles from both the sun and outer space. The magnetic field is our primary defense against them, hence the existence of the van Allen belt. Unless the 'flip' was very fast, our environment would be uninhabitable. We could survive underground, or in well-shielded buildings, but any exposed electronic equipment would likely be fried and electromagnetic communications would be impossible. Think of the worst solar flare you can imagine and up it a couple of orders of magnitude.
    As for what causes the reversal, and how it acts mechanically, I haven't a clue.
  21. Jul 21, 2005 #20
    Could you please expand on this idea; how or why you believe the magnetic field is caused by slowing down of time. .

    Last edited: Jul 22, 2005
  22. Jul 22, 2005 #21
    Although I currently believe my prior assumption was incorrect and that I am way over my head, the main reason I thought this made sense was because of the descripancy between objects speeding up and beginning to retain wavelike characteristics. The wave created by the expanded electron field of activity would act as the magnetic field. To me at least it seemed that time slowing down and an object taking on wavelike characteristics went hand in hand.
  23. Jul 22, 2005 #22


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    Nor does any one else on the planet !
  24. Jul 22, 2005 #23


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    Scott, you do not have to justify your previous statements. We accept them as misinformed thoughts that we hope you will correct by asking asking questions, and learning science the correct way - the way that takes time, effort and dedication.

    There is no physics in that last statement, so please stop, read and learn.
  25. Jul 23, 2005 #24
    Some requirements for a magnetic field according to the dynamo theory.

    (1) There must be a liquid or molten lava. In earth's case the the inner core is solid and much hotter then the outer core which is a hot fluid. The fluid near the inner core gets much hotter and then will become less dense and rise to the top. Once it gets hot it will rise towrads the upper part of the outer core. When it reaches the top of the outer core it cools and becomes more dense and falls to towards the inner core. This convection cycle continues.

    (2) There needs to be energy, mainly heat, which is thought to have been there since earth's birth. This energy is used to fuel the convection cycles.

    (3) There needs to be rotation or angular velocity about an axis. This angular velocity will produce a Corrialis force that will cause a sort of spiral path for the convecting molten lava. Think of taking a step radially outward in a merry go round. Although the angular velocity is constant, the further you move (or the further the molten lava moves) away from the center the faster the linear velocity will be.
  26. Jul 23, 2005 #25
    ehm,... not lava.

    but LARVAE ......

    he he heh...
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