Re: Earths Magnetic Field
Posted by Mike Kremer on Feb 02, 2004 at 17:26
(62.188.48.74)Re: Earths Magnetic Field (Gary Vandergrift)
Mercury in fact has a very weak magnetic field,
inspite of the fact that it is very dense, meaning that its core is probably mainly iron.
While Venus dosnt appear to have a magnetic field at all.
Its difficult to know what conditions were needed to start our own Earths magnetic field.
For instance were everything inside the Earth to rotate at the same speed, one wonders how a sustained magnetic field could start up in the first place.
Its more likely that Earths internal conditions arose similar to an automobile dynamo. Where a very small residual magnetic field in the dynamo's
metal plates, induces an small electric current within its field winding....that adds, and reinforces the magnetic field when its field winding is rotated...ad infinitum.
In our Earths case, a very slight difference in rock or mantle speeds could have caused a small voltage to produce the same initial effect I have described above....to started the magnetic field we see in the earth today. The "wires" that produced the current to start off the Earths magnetism, might well have been, salt water between hot rocks, or even molten Quartz and Sand ie Glass. (Glass is a very good conductor when molten) etc . Voltage/Current contributions to make our iron core magnetic? No one is quite sure exactly how.
Molten iron cannot normaly hold a permanent magnetic field....but the fact that our Earths iron core is highly compressed....may make
all the difference.
Note that the output of an automobile dynamo, can be instant reversed just by flashing the field winding with a small voltage. Which has similarities to our Earths pole changes?