MAGNETIC FIELDS OF THE TERRESTRIAL PLANETS
In general, magnetic fields are produced by electrical currents. There are
at least two ways in which to get magnetic fields which may be
relevant to planets:
- there can be large-scale electrical currents
- there can be something analogous to a bar magnet in the planets
Both of the above produce magnetic fields with the
familiar shape of a bar magnet:
Amazingly enough, if you look at the magnetic field of the Earth and at
local regions on the Sun,
the field shapes are very similar to that of a simple bar magnet.
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Magnetic Fields and the Interiors of Terrestrial Planets
The interior of the Earth (and most of the other Terrestrial planets) is
too hot for a permanent bar magnet to exist. So, in order
for the Earth to have a magnetic field, it seems as if the interior of the
Earth must be able to support strong electrical currents. This suggests that
the core of the Earth should be something like liquid (molten) iron.
This important property of the core of the Earth thus follows
simply from the fact that the Earth has a reasonably strong magnetic
field! (There are other issues involved, however.) |