Ocean Currents Proposed As Cause of Magnetic Field

pjt33 notes a recently published paper proposing that ocean currents could account for Earth's magnetic field. The wrteup appears on the Institute of Physics site; the IOP is co-owner, with the German Physical Society, of the open-access journal in which the paper appears. This reader adds, "The currently predominant theory is that the cause of Earth's magnetic field is molten iron flowing in the outer core. There is at present no direct evidence for either theory." "Professor Gregory Ryskin from the School of Engineering and Applied Science at Northwestern University in Illinois, US, has defied the long-standing convention by applying equations from magnetohydrodynamics to our oceans' salt water (which conducts electricity) and found that the long-term changes (the secular variation) in the Earth's main magnetic field are possibly induced by our oceans' circulation."

Comments

Could be...

[houstonbofh]

There is enough junk floating on the oceans that the currents could be ferrous.

I may be wrong, Im not an astrologer

[edittard]

Aren't there planets that do have magnetic fields, but don't have oceans? And aren't there moons that are the opposite case?

Re:I may be wrong, Im not an astrologer

[Creepy Crawler]

The idea of the ocean under Europa is that of an educated guess based upon tidal forces between Jupiter, and the fact that surface composition of Europa is frozen water. Flyovers have taken spectral pictures indicating that fact. They also have taken magnetic force readings and determined that any form of magnetosphere was Jupiters creating.

Ganymede has a liquid iron core, from which I dont understand how they figured that out. However, many sources say so, including NASA. And it's noted by the natural color of 'streaking on the ice' that the moon does have its own magnetosphere. And it was measured by Flyovers. It's strange that it still has a liquid iron core, al most over planets have frozen. The assumption is that Jupiter tidal forces have insulated it.

We dont need to understand why and how a liquid iron core creates a magnetosphere. We CAN measure more data points to see if our hypothesis matches with known facts. And this water-creates-magnetosphere seems debunked.

Re:I may be wrong, Im not an astrologer

[Korin43]

I wonder if the idea that Ganyemede has a liquid iron core is based on the assumption that only liquid iron cores cause magnetic fields?

Re:I may be wrong, Im not an astrologer

[vulpinemac]

Mercury has a magnetic field, which quite surprised planetary scientists when it was first discovered by MAriner 10, as the prevailing theory at the time was that Mercury's small size would have led to its core solidifying by now and stopping the dynamo that generated the field.

There's obviously a lot we don't know about planetary magentic fields, and I wouldn't want to judge the entire theory just by something I read on Slashdot, but I find it hard to understand how oceanic currents could account for Earth's magnetic field but not for Mercury's.

One piece of logic disrupts the idea that Mercury would have a solid core... It's proximity to the sun gives it a surface temperature hot enough to melt some metals. Granted, the opposite side of Mercury is also the coldest place in the Solar System (due to the planet's lack of atmosphere and equal lack of rotation.) This could, conceivably imply a solid core. However, just like boiling water, if you heat one side and leave the other side cold, you create a thermodynamic flow which could generate a magnetic field even without an orbiting moon to create the tidal current in that core.

Re:I may be wrong, Im not an astrologer

[GIL_Dude]

Current flow causes magnetism. You can demonstrate that with a non-magnetic copper wire and a battery. The copper doesn't suddenly become "iron like" and have a crystalline structure that responds (is attracted by) to magnetism. It is simply the current flow that causes this.

In much the same way, the molten iron theory is more around currents (fluid currents) causing electrical currents in the core. These electrical currents then cause the magnetism.

Nobody is saying that the iron itself is magnetic (because then it would be magnetite and not iron anyway).

Just last night...

[Anachragnome]

Just last night there was an interesting show on television that focused on the subject of magnetic fields associated with planets.

There was an experiment covered in the show that was essentially a large, hollow orb filled with liquid sodium (a substitute for the iron at Earth's outer core. It is impossible to reproduce the pressure and heat of our Earth's guts in such a small scale experiment) which was then spun at a comparatively equal rate to that of Earth. The orb began producing strong magnetic fields.

I somehow doubt that if the same experiment were to be reproduced solely with a thin layer of salt water on the surface (and no sodium inside) that it would produce such strong magnetic fields. That being said, while the thought of Earth's magnetic field being produced solely by the water on the surface is interesting, personally I think it is more then likely a combination of the two factors rather then one alone that produces our protective magnetic field.

In addition, I wonder if the flux in ocean water levels, historically speaking, coincides with the strength and direction of past magnetic fields as recorded in ancient lava flows. If so, this would seem to back up the theory proposed in the article.

Re:Just last night...

[db32]

[Citation Needed]

Seriously...please do. I was aware of the whole molten sodium ball thing because I remember that spinning 13 tons of molten sodium could be a REALLY bad idea. However, the last I saw of it they were still preparing and had not actually done anything yet.

Also...TFA isn't saying the field comes from water, it says variations in the field come from water passing through the main field. In typical /. fashion the summary is nonsensical crap.

Pseudoscientists attend!

[rlseaman]

Note how this dishes the favorite argument of pseudoscientists, who always (always, always) claim that the scientific "establishment" refuses to hear evidence that conflicts with accepted wisdom. Rather - to the extent that such an establishment can be said to actually exist - science will entertain any sort of extreme argument, as long as it is cogently - and entertainingly - presented. To overturn competing theories extreme arguments ultimately demand extreme evidence, however.

Re:Pseudoscientists attend!

[osu-neko]

Science has always reserved its greatest accolades for those who prove what came before to be wrong, and every scientist in the world knows the best way to become famous is to prove everyone else wrong. Nevertheless, pseudo-scientists always argue that scientists have some vested interest in preserving the current order (and thus dooming their careers into obscurity when they could have become famous Nobel prize winners). This argument has never made any sense, but that doesn't stop them from making it. So, one more example won't make any difference to them -- people who advocate a bad argument that runs counter to evidence are not dissuaded by more evidence.

Language matters

[Mr_Chang]

"The currently predominant theory ...of Earth's magnetic field"

To be certain, there are NO 'theories' for Earth's magnetism, only a variety of HYPOTHESIS'S.

Once again the term theory is being misused for HYPOTHESIS. It is a great disservice to science and scientists to not understand the definition and implications for both terms.

A worker whose research achieves the level of Theory is among the 'Nobel class' of scientists. Therefore the term should be used properly and with some reverence.

So before we go any further, would someone venture to post the scientific definitions and usage for these two terms, hypothesis and Theory.

Thanx

Re:Polarity switch

[Anonymous Coward]

It'll be the magnetic North pole... North just wont be where you think it is.

Re:Simply solved

[Lupulack]

I didn't say there was no iron at the core of the sun, only that there wasn't a great deal of it, at least in comparison.

And to quote the article linked, ''If secular variation is caused by the ocean flow, the entire concept of the dynamo operating in the Earth's core is called into question: there exists no other evidence of hydrodynamic flow in the core.''

So the only evidence of flowing iron at the earth's core causing the earth's magnetic field is ... the existence of the earth's magnetic field itself. That's a bit circular, isn't it?

Re:Polarity switch

[pnewhook]

Well magnetic north has moved over 1100 kilometers in the past 100 years, and the motion is accelerating. It is currently moving about 40km per year.

God built the world for man...

[TapeCutter]

Imagine a puddle waking up one morning and thinking, 'This is an interesting world I find myself in, an interesting hole I find myself in, fits me rather neatly, doesn't it? In fact it fits me staggeringly well, must have been made to have me in it!' This is such a powerful idea that as the sun rises in the sky and the air heats up and as, gradually, the puddle gets smaller and smaller, it's still frantically hanging on to the notion that everything's going to be alright, because this world was meant to have him in it, was built to have him in it; so the moment he disappears catches him rather by surprise. - D. Adams.

Re: Rejecting a Hypothesis

[anachronous diehard]

He also says:

There is little doubt that these conclusions will be met with skepticism. And so they should: the results presented by no means constitute a proof. But the possibility of direct connection between the ocean flow and the secular variation of the geomagnetic field is bound to stimulate further research, especially in view of the implications for the question of the origin of the main field.

I think Mr. Ryskin is well aware that he hasn't presented enough evidence to refute the prior hypothesis. He's only pointing out that secular variation has been considered important evidence supporting the dynamo theory. An alternate explanation for the variation wouldn't necessarily falsify the dynamo theory, but it could take away supporting evidence.

But he is correct that this should stimulate further research. His paper mentions enough analytical simplifications and limitations in the source data to suggest thesis topics for an army of grad students. I'm sure there will also be much thought about how the dynamo hypothesis might be independently confirmed.

Re:But this would mean?!?!?!?!?

[damburger]

Mars also has much lower gravity; basically what determines loss of volatiles is if the radiation impacting on the top of the atmosphere can give the molecules escape velocity. The actual mechanism is a bit more complicated than that, but is ultimately bound by conservation of energy.

Mars also didn't lose all its atmosphere to space - some froze as dry ice.