Earth Magnetic Field: the Dynamo Theory
Last week I had a conversation with Mike about the magnetic poles. I explained to him that the poles tend to go walkabout. The North magnetic pole moves from North Canada towards Siberia at about 55 – 60 kilometres per year. Then Mike asked: is there a link between the North and South magnetic poles positions?
No but yes. On the “no” side it can be said that over a period of time one pole can be relatively quiet while the other one runs. On the “yes” side the poles are a manifestation of the Earth Magnetic Field, so the cause of their existence and movements is the same.
Many years ago
scientists – including Einstein – thought that the totality of
the Earth formed a permanent magnet. But since then it was observed
that the Earth magnetic field force varied and that its polarity has
changed many times in the distant path. A permanent magnet can lose
strength over time, but it can’t change polarity. You need
something like an electromagnet. And sure enough the Earth outer
core, located about 2900 km under the surface, looks like one of
those, or rather like a bunch of them loosely coupled together.
The Dynamo
References:
Outer Core: https://www.nationalgeographic.org/encyclopedia/core/
Dynamo theory: https://en.wikipedia.org/wiki/Dynamo_theory
References:
Outer Core: https://www.nationalgeographic.org/encyclopedia/core/
Dynamo theory: https://en.wikipedia.org/wiki/Dynamo_theory
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