Earth's magnetic field collapsing!

[Ned]

Originally posted by gopher
Hmm, magnetic field starting to collapse around 1840's.
Marx and Engels start to develop what would later be known as socialism/communism around the 1840's.
Conclusion: Commies cause Magnetic problems.
Solution: Throw all commies out of helicopters, no more magnetic problems.
Benefits: No more magnetic declenation

Nah! It had to be the gold rush moving all that metal out of Califonia.

[Ned]

Originally posted by Big Crunch


I don't know how the Earth's magnetic field is supposed to flip but I do know how it supposedly happens in the sun's life cycles, and I'd imagine its a similar process on Earth.

Simply put, the sun's core is made up of several layers that rotate at differing speeds at differing latitudes and altitudes, each layer creating a different strength and orientation of magnetic field in each part of the sun. Effectively these fields superimpose upon each other and produce the external Heliospheric magnetic field that we can measure. Over time the alignments of these field changes, tightening and stretching the field strength to a maximum (visually the field lines look like the wringing of a towel tighter and tighter). Once a maximum is reached the field strength weakens again as the various magnetic fields of each part of the sun realign, and then eventually begin to unalign in the opposite direction.

There is no changing in direction of the flow or speed/momentum of the various parts of the sun though, just as there is no change in the rotation or motion of the Earth as it passes through the seasons from Spring to the the Summer (maximum) and then back trhough Autumn to the Winter (minimum). The solar cycle lasts for 11 years and is very regular.

At a guess the Earth's magnetic cycle is an erratic copy of the suns.

I am trying to visualize this, but frankly, I'm struggling. Can you draw a picture of how you can get relatively stable North and South fields of approimately equal intensity with fields in the directed between North and South during short periods of instability that occur during a flip?

[MrWhereItsAt]

Originally posted by Ned

Could this be a conservation of momentum issue? The magnetic field is a byproduct of currents of molten iron whose flow may be precessing to conserve momentum in some sort of environment. Since the period seems to be in the 100s of thousand of years, this suggests that the momentum that is being balanced is the solar system, does it not?

I don't know how much coupling you would have to the rest of the solar system, given the huge distances involved, and the fact that magnetic fields are weak, particularly at large distances. They are far outmatched by gravitational field effects at the distances we are talking about. Of course there would be SOME momentum transfer, but it might be too smal too be noticeable and thus it would be surprising if it led to reversals.

Originally posted by skywalker

I remember several Discover articles about a theory that it the core wasn't, in fact, nickel-iron. Rather, the guy thought it was uranium and the field was caused by its radioactive decay. The article said this accounted for the reversals too (I'm not sure how).

sky, there may be some confusion here. This may just be a radical new theory I have not heard, but it is widely accepted that the source of heat in the Earth that led to the flows of magnetic liquid in the first place are from the radioactive decay of elements within the Earth. Otherwise we would be sitting on a ball of rock that cooled ice-cold a few hundred million years (at most) after it was formed.

Assuming the Uranium was created during the planet's formation, a majority of it would have decayed to lead by now. Although it is possible Uranium DID make up the core of the planey, its half-life means that around 50% of it would have decayed to stable lead and given off the heat that is still there today.

Originally posted by Big Crunch
Simply put, the sun's core is made up of several layers that rotate at differing speeds at differing latitudes and altitudes, each layer creating a different strength and orientation of magnetic field in each part of the sun. Effectively these fields superimpose upon each other and produce the external Heliospheric magnetic field that we can measure. Over time the alignments of these field changes, tightening and stretching the field strength to a maximum (visually the field lines look like the wringing of a towel tighter and tighter). Once a maximum is reached the field strength weakens again as the various magnetic fields of each part of the sun realign, and then eventually begin to unalign in the opposite direction.

I imagine this is the case, and reversals certainly do not occur due to a huge wholesale change in flow within the Earth, but as you say it is only the NET field we see, from the superposition of many different fields. Of course you can get as complex as you like with these fields until you are summing the contribution from each individual dipole (and that's damn near impossible to do with only three of the damn things!) at the molecular level. If every one of these changed by a minute amount you may see a set of changes that leads to a reversal in the superimposed field.

[Kramerman]

so what exactly is it that keeps the core hot? where does all that energy come from?

[Drake Tungsten]

so what exactly is it that keeps the core hot? where does all that energy come from?

A natural nuclear reactor at the center of the earth.

[MrWhereItsAt]

Basically, yes. Radioactive elements like Uranium and Thorium decay to form products with lower mass numbers. In doing so, in order to satisfy conservation of energy, some of that energy is lost as heat and radiation. This is what keeps the Earth's insides hot.

[Dis]

and it has good insulation from the cold space as well

[Ned]

Is it the hot metal or the flow of the hot metal that creates the field?

[Kramerman]

movement of the metal. has somethn to do with faraday's stuff in physics, i believe.

anyway, it is very suprising to me that radioactive decay could provide enough energy to melt trillions of tons of rock and continue to heat it for billions of years. sure its well insulated, but.... i dunno. sure must have been a lot of radioactivity down there, cause of what i know of radioactive decay reactors is they arent all that powerful(use em on satelites and stuff). but then again i sont really know what im talking about

[Dis]

I'm not sure if radioactive decay is the right answer. Even with the elements with the longest halflives would have decayed by now you would think.

I'm not entirely sure what goes on down there. I don't think it's fission or fusion- there isn't dense enough material for that I'm sure.

this may be something to look up.

[CerberusIV]

It is radioactive decay. The earth had a lot of heat from its formation and radioactive decay has kept it topped up since then. So the decay didn't have to melt the core, only keep it liquid. It is slowly cooling and the generally accepted idea AFAIK is that there is a liquid outer core where the magnetic fields are generated and a solid inner core which is presumably growing slowly.

IIRC there are only four radioactive elements with sufficiently long half lives to still be making a contribution. Potassium is one and I think one of the Uranium isotopes and Thorium were others but can't remember the last one.

Mars research over the next few decades may shed some light on this as Mars's core cooled a long time ago (that's why plate tectonics never really got going on Mars) and may indicate what will eventually happen on Earth.

[Kramerman]

i see, well that does make more sense

[MrWhereItsAt]

Originally posted by Kramerman
movement of the metal. has somethn to do with faraday's stuff in physics, i believe.

Lenz's law I think (though I may have them the wrong way around!). The metal flowing means the electrons within the metal are moving (well, to put it simply), which is a current. Since the currents travel in a circular path around the core, this amounts to an induced magnetic field through the middle of the loop the currents form.

[/QUOTE]
anyway, it is very suprising to me that radioactive decay could provide enough energy to melt trillions of tons of rock and continue to heat it for billions of years. sure its well insulated, but.... i dunno. sure must have been a lot of radioactivity down there, cause of what i know of radioactive decay reactors is they arent all that powerful(use em on satelites and stuff). but then again i sont really know what im talking about [/QUOTE]

Keep in mind these 'radioactive decay reactors' are many trillions of tons smaller than the natural one in the Earth. The Earth weighs almost 6x10^25 kg. If only a quadrillionth of this was radioactive, that's still 6x10^10 kg of radioactive material.

[Ned]

But, Mr. where it's at, since the Earth's core rotates only in one direction, why does the magnetic field flip if it is the rotation of the electrons that cause the field.

[MrFun]

I'm more interested about the asteroid that's swinging by in 2014.

[CerberusIV]

Originally posted by Ned
But, Mr. where it's at, since the Earth's core rotates only in one direction, why does the magnetic field flip if it is the rotation of the electrons that cause the field.

Not that simple. There are convection cells in the liquid core so material moves between different depths and the overall field is the result of many different fields from the different movements in the core.

[Ned]

CyberusIV, wouldn't the core also rotate the same as our atmosphere - with the flow nearer the poles being opposite that near the equator?

[-Jrabbit]

Originally posted by MWIA
Some solid Earth scientists are starting to believe in just such a dual-layer outer core model, but again, this is all just guesswork with computer simulations thrown in.

All I know is, that dual-layer outer core model produces one helluva golf ball!
God bless those solid Earth scientists! Fore!!

[Sarxis]

Originally posted by Ned


Actually, if we do not have data prior to 1845, we may not know what the maximum field is. We might be far below the 90% of maximum that the story suggested.

They actually can tell what the magnetic field was like from samples dug out of the earth (fossils and geologic specimen). The magnetic field of the time polarizes elements in the sample, showing direction and magnitude. They use volcanic remains a lot because of its high metal content and nature to cool rapidly, conserving the polarization.

During 'flipping', some samples showed substantial field shift within 24 hour spans, when the field is in major flux globally.

[st_swithin]

Platinum jewelry is outselling gold jewelry these days. How much of a margin of conductivity does Pt have over Au? I wonder if there's a connection...

[Q Classic]

silver's still the best conductor.

[st_swithin]

Yeah, but it's brittle. Copper's good too, but it oxidises too readily. Pt is brittle too. I just know that Pt is a little more conductive than Au. And silver apparently doesn't convey the 'bling' quite as well as Pt.

[Q Classic]

silver is shiny. what more bling could you want?

[st_swithin]

Hey man, I don't create the trends, I just observe them. If it were up to me, we'd all be wearing head-to-toe neon day-glo a'la 1980's new wave - bada bling!

[Q Classic]

i'm glad you're not in charge.

[st_swithin]

Oh, you should be. You should be.

[Zero]

I wish I was in Chi...
:9

[CerberusIV]

Originally posted by Ned
CyberusIV, wouldn't the core also rotate the same as our atmosphere - with the flow nearer the poles being opposite that near the equator?

I don't remember all the details, it is a few years since I studied this, but the outer core behaves as a liquid and the flow pattern is complex. Also it is affected by whether there is continental or oceanic crust at the surface as continental crust is thicker and insulates the heat flow better so it is slightly hotter under the continents. The hotter is it the more easily it flows and so that affects field strength. Things like plumes causing hot spots like Hawaii complicate things further.

Apologies for a less than full explanation, it is a developing area of science involving a lot of research and the way it is understood is changing fairly rapidly.

[Ramo]

I recently read some stuff about mantle convection. Apparantly, it has a whole lot to do with the Earth's magnetic field. However it's a ***** to understand since Navier-Stokes governs it (and apparantly an inviscid flow is somehow a good approximation hmmm: - gotta love fluid dynamics).

[Dauphin]

Originally posted by Anun Ik Oba

During 'flipping', some samples showed substantial field shift within 24 hour spans, when the field is in major flux globally.

I have a hard time believing a science that deals in aging rocks and fossils to within thousands of years can measure the change in global flux to within a day.