A question about the Dynamo Theory

[zapnthund50]

I'm studying Dynamo Theory, and have just a few questions. Today's theory says that currents in the molten outer core of the Earth give rise to magnetic fields. Now it would seem that the theory does not mean "molten iron currents", since together that is an electrically neutral substance, but rather "electrical currents", since it is known that a moving electrical charge generates a magnetic field. If this is true, then what induced the electrical currents in Earth's core? Am I grasping the main scientific concept behind field generation, or is there something else I'm missing? Thanks!

 

[davenn]

I'm studying Dynamo Theory, and have just a few questions. Today's theory says that currents in the molten outer core of the Earth give rise to magnetic fields. Now it would seem that the theory does not mean "molten iron currents", since together that is an electrically neutral substance, but rather "electrical currents", since it is known that a moving electrical charge generates a magnetic field. If this is true, then what induced the electrical currents in Earth's core? Am I grasping the main scientific concept behind field generation, or is there something else I'm missing? Thanks!

You have marked your thread with an "I" tag for undergraduate level education

what have you been reading in your research so far ? so we can gauge where you are at Dave

 

[zapnthund50]

You have marked your thread with an "I" tag for undergraduate level education

what have you been reading in your research so far ? so we can gauge where you are at Dave

Hi Dave,

My appologies, the thread was not meant to be marked undergraduate, but rather basic level. Thanks for pointing that out. Can you comment on the matter of currents?

 

[davenn]

Hi Dave,

My appologies, the thread was not meant to be marked undergraduate, but rather basic level. Thanks for pointing that out. Can you comment on the matter of currents?

no problems :)

since I don't know what you have been reading ?
have you read this from Wiki ?
https://en.wikipedia.org/wiki/Dynamo_theory

or this
https://web.archive.org/web/20070221094040/http://setiathome.berkeley.edu/~pauld/etc/210BPaper.pdf

or this
http://www.phy6.org/earthmag/dynamos.htm

or this
http://farside.ph.utexas.edu/teaching/plasma/lectures/node70.htmlthat will keep you occupied for a while Dave

 

[zapnthund50]

no problems :)

since I don't know what you have been reading ?
have you read this from Wiki ?
https://en.wikipedia.org/wiki/Dynamo_theory

or this
https://web.archive.org/web/20070221094040/http://setiathome.berkeley.edu/~pauld/etc/210BPaper.pdf

or this
http://www.phy6.org/earthmag/dynamos.htm

or this
http://farside.ph.utexas.edu/teaching/plasma/lectures/node70.htmlthat will keep you occupied for a while Dave

Dave,

Thanks for all the links. I've thoroughly read each one, and I can say they proved a solid framework for beginning to understand Dynamo Theory. I had read the wiki article before, but the paper on the subject proved invaluable.

Based on what I've learned, the physics of DT can be simplified to the following: A conducting fluid circulates (convection, Coriolis effect) through an existing magnetic field. Moving this conductor (in our case, mostly molten iron) across magnetic lines of force forces a current to be generated. This current will have its own magnetic field. Of course the theory is much more complicated than that, but from what I can gather, this is the physics behind DT. (I think the wiki article was somewhat confusing, as it made no distinction between the physical current of molten iron, and the electrical current flowing through it.)

The only question I have left is, where does the original "bootstrap" field come from? Only one of the links ventured to guess, saying vaguely that weak magnetic fields are always present. All this just makes me want to study one of the many models that must have been made, but I have no idea where to find those. Anyway, thanks for your help.