Who Knows Why Earth has a Magnetosphere?

[why06]

Personally I was surprised by how much we do not know about the mechanism that creates Earth's magnetic field or the reason for the reversals.

There are two main theories explaining Earth's magnetic field:

- Dynamo Theory: states Earth's magnetic field is caused by the convection of conductive fluids within Earth's core, most likely liquid iron. Apparently the reversals are an "inherent aspect of dynamo theory"-Wikipedia. What ever that means. What I do know is that the upper crust of Earth prevents the convection of the molten iron. However Dynamo Theory is the most popular theory of the moment.

-- geomagnetic excursions: Some scientists believe that a change in reversal is caused by an external impact such as a comet collision. They also figure that the magnetic field must be "stopped" and then turned back on.

- Georeactor Theory: Fixes some of the problems with dynamo theory because it does not require convection. fusion reactions deep in the core are the cause of the magnetic field. This theory was originally designed to explain the magnetic fields of outer planets such as Jupiter and Saturn. Because extreme pressures and temperatures are needed to create fusion many scientists are skeptical that the necessary conditions could be obtained in a planet Earth's size. This theory has much less support than dynamo theory for this reason.


What does have strong evidence is that the magnetic field has reversed before: http://en.wikipedia.org/wiki/Geomagneti ... ast_fields Field reversals can be detected by studying the magnetization of iron rich minerals from different time periods, since these minerals are influenced by the ambient magnetic field of the time.





So we know that their is a field reversal but we don't know why there is a reversal?
- Magnetic Portals: Recently (by recently I mean October of last year) it was discovered that the magnetic fields of the sun and Earth connect about every eight minutes forming a sort of magnetic portal (about as wide as Earth allowing high energy particles to cruse through energizing Earth's Magnetic field. As of know no one really knows what causes them, but its to early to be certain but could these FTE's (flux transfer events as they are being called) be the cause of our pole reversals?

 

[MeteorWayne]

No on that last part.

 

[why06]

Then what do u believe is the cause of the reversal then. The last possible scenario has just as much evidence as any of the other ones, which is none. What do you think about the other possibilities. "No on that last part" is not saying much. This was really a post to start a discussion about the causes of Earth's magnetic field.

 

[MeteorWayne]

If you research the Geodynamo theory a little more, you will find that the self regenerative qualities of that theory explain reversals reasonably well. Of course, at this point, we don't know for sure, but the other theories you suggest have little or no support (especially for reversals).

 

[3488]

Also it's worth remembering that the Earth has a dual layered core, the inner one solid the outer one molten & convecting. It is also interesting to see that Jupiter's moon Ganymede & now Mercury both appear to also have dual layered cores, also have active internally driven magnetospheres.

There appears to be some relationship that the inner core is rotating slightly slower than the rest of the Earth, & this generates a shearing action (possibly also generating additional heating at the base of the outer core) with the base of the outer core causing it to convect. Hot molten iron rises, then cools slightly as it ascends then sinks, then reheats & the process repeats. Over time this will decline as more iron from the outer core precipitates & solidifies on the inner core (meaning that over billions of years, the Earth will end up with a cooler single large core).

It is thought that since the formation of the Earth, 7% of the original outer core's iron has solidified, so it seems likely the Earth will keep a magnetosphere of some sort, till the Sun turns into a red giant & possibly destroys the planet (seeing as 93% still remains after 4.6 GY).

Spinning & convecting molten iron generates a magnetic field. Earth's field is certainly generated by a dynamo effect. One possibilty regarding magnetic pole reversals is the the outer core displays differential rotation, the poles rotating very slightly slower then the equator (just like the Sun, but the difference is far smaller lasting over a vastly longer period).

The strange thing is, that Venus appears to only have a single core as does Mars & both lack internally driven magnetospheres. This appears to be more than just a co-incidence.

Andrew Brown.

 

[xXTheOneRavenXx]

The strange thing is, that Venus appears to only have a single core as does Mars & both lack internally driven magnetospheres. This appears to be more than just a co-incidence.

Andrew Brown.

I wonder if it would have anything to do with either composition or core density.

 

[andrew_t1000]

One thing I have always wondered, in fact every time I switch on my soldering iron,
(it's a Weller TCP. It has a Curie Point magnet that controls the temperature)
Is how does molten iron and nickel still have magnetic properties?
If you melt some iron with an oxygen/acetylene torch, a magnet won't attract the molten iron.
I had to try it just to be sure.
Could someone please clear this one up for me?