Naked Science Forum
General Science => General Science => Topic started by: colorshapetexture on 11/04/2013 17:48:42
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If magnetism is lost when the magnetic material is heated.
The curie temperature for a low carbon steel is 770oC or 1390oF.
And the center of the earth is beleived to be much much hotter.
Then isen't all magnetism lost or non existant at the core?
Earths diameter at the equator is 7,926.28 miles. We have seismic refraction measurements that put the thickest parts of the continents/crust at 35 miles thick. Understanding the ocean crust is not as thick but the H2O is very conductive especially with high salt content. For a base lets say the the whole earth has a "cool" enough shell that it can and is magnetic.
So most of the earth would be non magnetic. Unless Alfven waves and plasma was present?
The sun is 10s of thousands of degees yet is magnetic? It ejects plasma.
Simply earth without the solid crust?
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If magnetism is lost when the magnetic material is heated.
The curie temperature for a low carbon steel is 770oC or 1390oF.
And the center of the earth is beleived to be much much hotter.
Then isen't all magnetism lost or non existant at the core?
The Earth's magnetic field is like an electromagnet : a moving electrically conductive fluid of liquid iron , not like a solid-iron permanent-magnet. That this liquid iron is above the Curie temperature does not stop it conducting electricity and generating a magnetic field when it moves ... http://en.wikipedia.org/wiki/Dynamo_theory
[BTW the Curie temperature is also pressure dependent ]
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Experiments have been conducted in a successful attempt to reproduce the dynamo effect in a conducting liquid. They have been able to reproduce chaotic reversals in the magnetic field, similar to what is seen in the magnetic fields of the Sun and Earth. One team used liquid sodium, a very reactive substance (otherwise used in advanced nuclear reactors)!
See http://physics.aps.org/story/v19/st3
...but I haven't been able to spot any recent stories after the announcement in 2007?
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Last I heard, the inner core was thought to be solid, in the form of iron-nickel crystals (and possibly some iron hydride and high-density transition metals such as gold, platinum, etc). It's about 2400km in diameter and 'floats' in a liquid metallic outer core of mainly iron & nickel.