# Why is a magneto-dynamo electro - magnetic system self - sustaining?

## Main Question or Discussion Point

A recent episode of NOVA, The Magnetic Storm, it had been said that,

"According to generally accepted theory -- the dynamo theory -- interactions between the churning, twisting flow of molten material in the outer core and the magnetic field generate electrical current that, in turn, creates new magnetic energy that sustains the field"

http://www.pbs.org/wgbh/nova/magnetic/

http://geomag.usgs.gov/faq.html [Broken]

http://www.psc.edu/science/Glatzmaier/glatzmaier.html

How can a magnetic field sustain an electrical field which sustains a magnetic field which.... ?

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## Answers and Replies

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Integral
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It is all in Maxwell's Equations The last 2 Faraday's law of induction and Ampere's law relate a time changing to space changing fields.

In both the LHS is a mathematical statement of a field which changes with location. The right hand side of each is a statement of a TIME changing field.

Faraday's law says that a space changing Electric field is the same a time changing Magnetic field.

Ampere's law says that a space changing Magnetic field is the same as a time changing electric field. This equation contains a term which attributes a contribution to the space changing Magnetic field is also made by an electric current density (J).

In propagation of electo-Magnetic signals energy is exchanged between the Magnetic and Electric fields as described by these equations.

Thank you.

Another question. Do you have any opinion on the periocity of
changes in magnetic pole orientation?
Why don't they occur at regular intervals (or in a pattern of changes which is at regular intervals?)

Could the slowing down of the earth have any effect, or is the irregularity inherent in the generation of electro-magneto currents?

In the PBS special they had discovered from probes that Mars has
no magnetosphere. They had also said that the magnetic field of the
earth is decreasing (which is what happens during magnet pole orientation changes). Do you suppose that Mars, which has no magnetosphere, may actually be in the process of changing polarities, (and has a long period)?

pole changes

i remeber reeading about the magnetic poles being controlled by nuclear reactions in the core.

they are suppose to wax and wain depending on how the nuclear reactions are doing, leading to pole reversal etc.

mars may very well be in the long part of the down phase

but what do i know

crossmodul8 said:
i remeber reeading about the magnetic poles being controlled by nuclear reactions in the core.

they are suppose to wax and wain depending on how the nuclear reactions are doing, leading to pole reversal etc.

mars may very well be in the long part of the down phase

but what do i know

Curious. Is this suggesting that the earth has at it's core nuclear activity?

Gokul43201
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S = k log w,

Are you an admirer of Boltzmann or a collector of trivia ?

LURCH
Science Advisor
pallidin said:
Curious. Is this suggesting that the earth has at it's core nuclear activity?
It is widely believed that radioactive decay is a major contributor to geothermal heat.

Regarding the periodicity of magnetic polar inversions, and the self-sustaining nature of magneto-dynamos, I have been following developments athttp://complex.umd.edu/dynamo/index.html [Broken] for some time, but the final model has yet to be built and operated.

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