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Q & A: Earth's hot core and magnetism

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Most recent answer: 12/15/2016
Q:
How does the Earth generate a magnetic field if the core is hot liquid metal and heat destroys magnetism?
- Jonathan Neville (age 62)
84117
A:

Heat destroys ferromagnetism, the alignment of the magnetism of nearby electrons due to the details of their quantum interactions. There can also be classical magnetism due to ordinary electric currents, like the magnetism you get when you run a current through a coil. The magnetism of the earth's core comes from large-scale classical currents. They're driven by the heat released by radiactive decay of elements in the core, but I don't understand the complicated process by which that stirs up the big currents. It involves the earth's rotation, which is why the magnetic poles are usually not far from the rotational poles (north and south).The liquid flow is part of the process. Like the sort of patterns that form in boiling water, the current pattern is unstable, so the poles sometimes reverse, with a period of reduced magnetic field during that reversal.

Mike W.


(published on 12/15/2016)

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