Bad News for Earth's Magnetic Field

jabex writes "Scientific American's website has an article about the overdue magnetic field flip. According to research published in the journal Nature, it could take anywhere from 2000-10000 years to complete. That's a long time without a protective magnetic field."

Comments

The Earth's magnetic field is overrated

[Rapid Home Offer]

Who needs the Earth's magnetic field, anyways? As long as I have my ozone layer, and my handy dandy lead codpiece, everything is going to be okay.

(Doesn't everybody have a lead codpiece?)

cautionary notice of threatened death.

[mkavanagh]

any mention of a certain bullshit hollywood production with the shittiest scientific basis for a film since the neverending story will result in death. of the poster. thanks for not getting yourselves killed.

no magnetic field, really?

[Bastian]

I'm no geologist, but it seems strange to me that in the process of a magnetic field reversal the earth's magnetic field would just go away for a few thousand years. Wouldn't the field just rotate over time, so that the magnetic north pole continues to drift until it is near the geographic south pole?

Re:no magnetic field, really?

[JGski]

It's apparently far more complex.

From what I've read on the web and seen on a PBS Nova program about the subject: during a flip the Earth's internal dynamo goes from ordered to chaotic. The movements is not just is a straight bee-line to the opposite side. The North pole, for example, has been drifting even of the last 30 years toward the south east. The field strength declines substantially and the magnetic fields change from bipolar (two poles: north and south) to multipolar ("poles" coming out of any which direction - the "Southern Anomaly" in the south Atlantic is apparently believed by some to be the onset of a tripolar field). When the actually collapse is imminent, these poles start moving quickly, as much as degrees of latitude or longitude per day or week.

Re:no magnetic field, really?

[therealmoose]

No, it's quite complicated (somewhat like a fluid system). Regions of the field spin around, strengthen, weaken, and drift around in complex 3d patterns for thousands of years according to the models (confirmed by geological finds). The net effect is that the field is significantly weaker (due to the lack of a uniform makeup, in part) and in some regions, some of the time, effectively nonexistant. It is not sufficient to deflect the radiation that it currently does while 'flipping'.

Re:no magnetic field, really?

[umofomia]

From what I've read on the web and seen on a PBS Nova program about the subject: during a flip the Earth's internal dynamo goes from ordered to chaotic.

Yep... I've seen this Nova too. It was pretty interesting. For the rest of you out there, here's a link to the show's web site, where you can also see an animation of a computer simulation of a polar reversal. During the reversal, the earth could have poles coming out of the equator even, and if you were able to witness it, you would even see auroras around those poles.

Re:no magnetic field, really?

[CheshireCatCO]

"None the less, I tend to like simpler solutions than a chaotic tri-poled earth magnetic field, or whatever currently is the explanation."

Yes, but surely you like an explanation that is *accurate* even more than you like one that is simple. I mean, I can think of simpler explanations for the striping quite easily. (Like, "There is no striping. These are not the droids you're looking for...") But they probably wouldn't reconcile with the various data very well. :-)

(Also, magnetic fields fall off as least like 1/r^3. The lowest order moment is a dipole, remember. At least until someone finds a magnetic monople, anyway.)

To get at the article you linked:

First of all, it suggests that the planets' fields are all oriented the same way with respect to their spins. Not true. See my post, above. Jupiter's field is oppositely oriented to that of Earth, for example.

It goes on to "point out" that Uranus's field is aligned with it's odd spin vector. Surprisingly little research with Google would have shown that to be very wrong. Uranus's spin and magnetic field axes are about 60 degrees apart. That's no where near alignment.

He (I'll assume that the author is male) procedes to blame large amounts of cobalt and iron in Earth's crust for the slightly off spin axis magnetic field axis. Large amounts? The overwelming majority of Earth's iron is in the core or mantle, not the crust. What is in the crust is fairly evenly distributed. It's hard to imagine that the symmetry is broken that much, isn't it? (Sorry I don't have the raw numbers for the distributation, but I doubt that anyone has worked it out.) But if the iron in the core wants to direct the field along the spin axis, how is the miniscule amount of iron in the crust going to "redirect" that field significantly over global scales? (Sure, you've got a bigger lever-arm at the crust than the core. But only by a factor of a few. We're being told that that offsets the massively higher concentration of iron in the core.) Also, why is Earth's field offset as well as titled? (No lever-arm helps you with that one.)

Another interesting error is the (apparent) assertion in the tidal breaking section that Earth will eventually spin 1/28 as fast to match the Moon's orbital period. That's half true, we will match the Moon's orbital period in about 5 billion years. (Just in time to be destroyed by the Sun's red giant phase. Yay!) But a simple knowledge of conservation of angular momentum tells you that we won't be spinning once every 28 days. It's more like a 89 day period, if you work it out. (Funny how he can use conservation of energy to apparently bolster his case when he wants to, but doesn't know what conservation of angular momentum is. While both are adhered to, with the latter it is much harder to "fake" a violation.)

Next up... mass extinctions. He claims that palentologists have determined that they (the extinctions, not the palentologists) occur every 32 million years. Hm. About five mass extinctions in the history of the Earth (the last 65 million years ago) are known (http://www.bagheera.com/inthewild/spot_massextinc tions.htm) spanning back 440 million years or so. That's 380 million years and 4 intervals between them. Quick math check... I get that that's one every 95 million years. (Is that what you get, too?) For proving that exctinction events aren't caused by impacts, that's pretty weak. (Based on the cratering record on the Moon, mainly, the calculated interval between mass exinction causing impacts is about 100 million years. Roughly speaking.)

Next bit of funniness. He claims that "Therefore a reversal in ion polarity would indeed reverse the Earth's magnetic field;" and then goes on to try to show that this is silly. Which is a strawman, since I don't know anyone who asserts that the ions will reverse polarity. How do you get ions to reverse polarity?? Unlike in chemistry, ions in astronomical contexts are essentially

Dipole to quadrupole to reversal...

[lcde]

I can't find the article on google right now, but the last time i read about this in between the reversal of earths magnetic pole it turns into a quadrupole or higher order for a couple of hundreds of years then it finishes.

Still we won't lose our magnetic field unless our core solidifies, but a field reversal or a higher order magnetic field will allow different polorization of solar winds and other EM noise that would be different that what we have now. We also might not be as well protected against the solar flares during the sun's cycle.

are we sure Halliburton

[morelife]

or one of its subsidiaries isn't doing this remotely?

Re:Can GPS substitute?

[bluGill]

Learn to navigate without a compass. I live in an area with many iron deposits, we learned long ago that a compass is not a reliable tool for navigation. We learn other tricks. (Starts at night, guesstimate the time and use the sun during the day). Combine that with knowing about what the land should look like and you can get close enough. Not as easy or are reliable a a compass in other areas, but it works.

Goodbye Van Allan Belt, Hello Cosmic Rays

[StateOfTheUnion]

The original linked article isn't very informative. There will probably be a period of no significant magnetic field while the field is reversing . . . Here's an article about a simulation that to everyone's surprise, actually predicted the reversal.

Goodbye Van Allan Belt, Hello Cosmic Rays . . .

Way Overdue

[jazman_777]

The magnetic field flip, the super-volcano in Yellowstone, the San Andreas Fault, the demise of SCO. Have I missed anything? A Red Sox or Cubs World Series winner?

Re:You sound as if you know what you're on about..

[CheshireCatCO]

Appart from the general off-topic nature of that rambling post, it shows a poor understanding of the data, unless someone has utterly failed to clue me in on some breaking developments in astronomy. (Possible, but my collegues like talking about their work too much for me to think that that's likely.)

You'd better show me a paper that suggest that gravitational redshift doesn't happen, because I have yet to hear of it. And since that'd be Nobel-quality work, showing that GR breaks down (where it should hold up), I'd be surprised if the research happened. In fact, I attended an entire comps on GPS. While GR was certainly discussed, since they need to take it into account for GPS to work, no corrections to that theory were mentioned. Seems sort of odd that the speaker would talk about GR without mentioning that it broke down.

And I have yet to see a steady-state model that matches the data very well at all. The whole "cosmic microwave background" thing is hard to get around. Since I just attended a lecture by a well-known cosmologist and he didn't say a word about the Big Bang being "broken", I will have to once again ask you to back up your rather grandiose assertions.

As for planetary magentic fields:

There are lots of ways that Mercury can have a fluid core, still. The most commonly argued one is to have more sulfur mixed in. This should lower the freezing point sufficiently to keep it molten still. It's also worth noting that Mercury has an unusually large core for its size. This might play in to things.

Mars lacks a global field (today) because it has almost certainly cooled off too far. (If we assume the same composition as the Earth, anyway.) This is supported by the lack of ongoing volcanism or tectonics, which also require a molten interior to proceed. However, in the past Mars *did* have a global field. This is quite consistent with the theory, since it would have been warmer inside.

As far as I know, no one has ever suggested that Venus's retrograde spin is the cause of the lack of a magnetic field. That's fairly silly, since the field doesn't know which "way" the planet is spinning anyway. (Magnetic field on other planets are can be found oriented both ways with respect to their planets' spins and we know that Earth's field has changed direction.) However, the astute person would have noticed that Venus does spin very, very slowly. This would generally lead to a small or non-existant field, since planet spin is thought to be tied in to the dynamo process. (There's a strong correlation between field strength and planet's angular momentum, for example.) Of course, Mercury only spins 3 times faster, but that's still something.

I'd also love to see your proported research showing field changes if 90 minutes or less. How in the heck do you DATE to that accuracy? You can't, unless you pretty much just watched it cool. (In which case, why didn't every compass on Earth notice the switch?)

No one is saying that we totally understand cosmology or magnetic dynamoes. But to suggest that we're "whistling in the dark" is to down-play the wonderful and careful work of far too many people to let you get away with saying that here. We might not have the details all down, but I'd say that we're doing alright on the theories.

punctuated equilibrium

[orn]

The fossil record shows that the Earth goes through periods of time where there is an incredible amount of speciazation - new critters pop into being very quickly. I've read other stuff that suggests that this is simply due to the die-offs: since there's a niche available, something moves to fill that niche.

Could this be a contributing factor or even a causative agent? The normally low error rate in genetic reproduction takes a big spike due to more particles getting through the Van Allen belts?