Magnetism of planets

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Main Question or Discussion Point

Like the earth, do other planets have magnetism?
 

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  • #2
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Every electron, by nature, is a magnet. If there are electrons there has to be magnetism.So I think there will be magnetism in other planets also.
 
  • #3
LURCH
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Mars seems to have almost no magnetic field at all, and the same for Venus. Mercury is the only inner planet besides us that seems to have one. The current theory is that having a magnetic field around a planet is dependant on having a metal core.

The outer planets have truely monsterous magnetosheres. Neptune's magnetic poles are so far out of alignment from its rotational poles that the planet looks like it could be used as an alternator!
 
  • #4
mgb_phys
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The current theory is that having a magnetic field around a planet is dependant on having a metal core.
Specifically a liquid metal core - which means a minimum size of planet to be big enough to have melted the core and large enough to keep it warm.

Jupiter has a very strong magnetic field, although it doesn't have any metal.
Under the extreme pressures at the centre of Jupiter, Hydrogen can behave a little like a metal.
 
  • #5
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Do we really have so little knowledge of the processes in our planets' core? (And when there is so much literature concerning models of neutron star magnetic fields..)

Is there an accepted model of why the liquid metal gives rise to the field?
 
  • #6
mgb_phys
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The overall mecahnism is known, conducing iron flows in convection currents creating effecively a dynamo.
The details are a little more complicated than a simple model of a symetric rotating neutron star.
 
  • #7
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The overall mecahnism is known, conducing iron flows in convection currents creating effecively a dynamo.
Really that simple? My dynamo experience does not lend me to expect that stirring a bowl of quicksilver should produce any magnetic field. Could you expand on how electrical charge is produced (if the mantle were initially neutral) and maintained (when convection sounds slow compared to the conductivity)?
 
  • #8
LURCH
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Specifically a liquid metal core - which means a minimum size of planet to be big enough to have melted the core and large enough to keep it warm.

Jupiter has a very strong magnetic field, although it doesn't have any metal.
Under the extreme pressures at the centre of Jupiter, Hydrogen can behave a little like a metal.
Although it clearly isn't size alone that makes this determination (Mercury has a magnetic field and Mars and Venus do not). And yes, it would be fair to say that nobody really knows why. It's amazing how much we don't know. But, regarding the models of magnetic fields of neutron stars; they are only models, and we do have models of planetary magnetic fields. We just can't get the models to match some of the observations.

A team of researchers at Maryland University are trying to buildhttp://complex.umd.edu/dynamo/index.html" [Broken] called a " geodynamo" to explore why the magnetic field apparently "flips" periodically.
 
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  • #9
But I wonder how hydrogen could behave like a metal in a high-pressure condition? What is the theory that leads to the magnetism inside the hydrogen core( if there is really a hydrogen core inside Neptunian Planet)? Hydrogen in normal condition exhibit diamagnetism, which mean it has very weak magnetic field.
 
  • #10
LURCH
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Nothin really fancy; when Hydrogen is significantly compressed, the electrons become free to rome from one nucleous to another. Once this happens, the element matches the definition of a "metal."

http://en.wikipedia.org/wiki/Metallic_hydrogen" [Broken] about that metal being achieved in a lab heer on Earth (at Livermore).
 
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  • #11
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Finally, ty for the confirmation.

I've been trying to relate the macro world to atomic world. I say that planets are like electrons in an atom. I claim that the magnetic strength is a function of spin. Heck, our solar system might be bonding with some the adjacent solar system by some outter planet that have strong magnetic field. Don't tell me i'm wrong. I can't take this. :)
 

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