Earth’s internal dynamo generates average field in outer core 50 times that at surface
A University of California, Berkeley, geophysicist has made the first-ever measurement of the strength of the magnetic field inside Earth’s core, 1,800 miles underground.
The magnetic field strength is 25 Gauss, or 50 times stronger than the magnetic field at the surface that makes compass needles align north-south. Though this number is in the middle of the range geophysicists predict, it puts constraints on the identity of the heat sources in the core that keep the internal dynamo running to maintain this magnetic field.
“This is the first really good number we’ve had based on observations, not inference,” said author Bruce A. Buffett, professor of earth and planetary science at UC Berkeley. “The result is not controversial, but it does rule out a very weak magnetic field and argues against a very strong field.”
The results are published in the Dec. 16 issue of the journal Nature.
A strong magnetic field inside the outer core means there is a lot of convection and thus a lot of heat being produced, which scientists would need to account for, Buffett said. The presumed sources of energy are the residual heat from 4 billion years ago when the planet was hot and molten, release of gravitational energy as heavy elements sink to the bottom of the liquid core, and radioactive decay of long-lived elements such as potassium, uranium and thorium.
A weak field – 5 Gauss, for example – would imply that little heat is being supplied by radioactive decay, while a strong field, on the order of 100 Gauss, would imply a large contribution from radioactive decay.
“A measurement of the magnetic field tells us what the energy requirements are and what the sources of heat are,” Buffett said.
About 60 percent of the power generated inside the earth likely comes from the exclusion of light elements from the solid inner core as it freezes and grows, he said. This constantly builds up crud in the outer core.
The Earth’s magnetic field is produced in the outer two-thirds of the planet’s iron/nickel core. This outer core, about 1,400 miles thick, is liquid, while the inner core is a frozen iron and nickel wrecking ball with a radius of about 800 miles – roughly the size of the moon. The core is surrounded by a hot, gooey mantle and a rigid surface crust.
The cooling Earth originally captured its magnetic field from the planetary disk in which the solar system formed. That field would have disappeared within 10,000 years if not for the planet’s internal dynamo, which regenerates the field thanks to heat produced inside the planet. The heat makes the liquid outer core boil, or “convect,” and as the conducting metals rise and then sink through the existing magnetic field, they create electrical currents that maintain the magnetic field. This roiling dynamo produces a slowly shifting magnetic field at the surface.
“You get changes in the surface magnetic field that look a lot like gyres and flows in the oceans and the atmosphere, but these are being driven by fluid flow in the outer core,” Buffett said.
Buffett is a theoretician who uses observations to improve computer models of the earth’s internal dynamo. Now at work on a second generation model, he admits that a lack of information about conditions in the earth’s interior has been a big hindrance to making accurate models.
He realized, however, that the tug of the moon on the tilt of the earth’s spin axis could provide information about the magnetic field inside. This tug would make the inner core precess – that is, make the spin axis slowly rotate in the opposite direction – which would produce magnetic changes in the outer core that damp the precession. Radio observations of distant quasars – extremely bright, active galaxies – provide very precise measurements of the changes in the earth’s rotation axis needed to calculate this damping.
“The moon is continually forcing the rotation axis of the core to precess, and we’re looking at the response of the fluid outer core to the precession of the inner core,” he said.
By calculating the effect of the moon on the spinning inner core, Buffett discovered that the precession makes the slightly out-of-round inner core generate shear waves in the liquid outer core. These waves of molten iron and nickel move within a tight cone only 30 to 40 meters thick, interacting with the magnetic field to produce an electric current that heats the liquid. This serves to damp the precession of the rotation axis. The damping causes the precession to lag behind the moon as it orbits the earth. A measurement of the lag allowed Buffett to calculate the magnitude of the damping and thus of the magnetic field inside the outer core.
Buffett noted that the calculated field – 25 Gauss – is an average over the entire outer core. The field is expected to vary with position.
“I still find it remarkable that we can look to distant quasars to get insights into the deep interior of our planet,” Buffett said.
The work was funded by the National Science Foundation.
Leif Svalgaard says:
December 18, 2010 at 3:10 pm
Carla says:
December 18, 2010 at 5:17 pm
…………….
What is happening in the Earth’s interior scientist can only speculate, so can the rest of us. I would be inclined to suggest that the geomagnetic field is generated closer to the surface than the deep down in the core. Circulation and vortex forming is governed by the laws of fluid dynamics. According to the present structure of the GMF, there could be 3 local vortices in the upper mantle two in the Northern Hemisphere and one in the South, each creating its own bar magnet. Jackson may be correct about separate circulating entities, but they are more likely to be conical shape then parallel cylinders, with tips of the cones somewhat eccentric, deep down in the core, inclined South American way.
http://www.vukcevic.talktalk.net/MF.htm
There you are, you seen it here first; another first for WUWT.
That should not be difficult to visualise. Doc is bound to say nonsense, but he routinely does that when short of good alternative reasoning.
vukcevic says:
December 19, 2010 at 12:50 am
Circulation and vortex forming is governed by the laws of fluid dynamics. According to the present structure of the GMF, there could be 3 local vortices in the upper mantle
Except that the upper mantle is not fluid. Jackson’s result is an observation, not an inference.
vukcevic says:
December 19, 2010 at 12:50 am
Leif Svalgaard says:
December 18, 2010 at 3:10 pm
Carla says:
December 18, 2010 at 5:17 pm
…………….
What is happening in the Earth’s interior scientist can only speculate, so can the rest of us. I would be inclined to suggest that the geomagnetic field is generated closer to the surface than the deep down in the core. Circulation and vortex forming is governed by the laws of fluid dynamics. According to the present structure of the GMF, there could be 3 local vortices in the upper mantle two in the Northern Hemisphere and one in the South, each creating its own bar magnet. Jackson may be correct about separate circulating entities, but they are more likely to be conical shape then parallel cylinders, with tips of the cones somewhat eccentric, deep down in the core, inclined South American way.
http://www.vukcevic.talktalk.net/MF.htm
~
One question Vuks after viewing the image at your link above. Why is it we never see that huge continent called ‘Antarctica’ at the south pole depicted in these intensity field maps?
Leif Svalgaard says:
December 19, 2010 at 5:35 am
…………..
Thanks for pointing the error, word ‘upper’ got in there unintentionally. Not in the link
http://www.vukcevic.talktalk.net/MF.htm
with a more detailed discription.
Anyway, wherever magma happened to be. Jackson has done some great work, but he is wrong about excentric cylinders, not possible in rotating sphere. Conical vortex can easily be initiated by Coriolis forces. See the link above.
Circulation and vortex forming is governed by the laws of fluid dynamics, and that is same for all fluids, including atmosphere and magma.
You may have a little problem here: the Earth’s stratosphere is subject to the same Coriolis force, and guess what; it does the same as the magma vortex, you may consider obvious alternative, the gmf has control of stratospheric vortex.
http://www.vukcevic.talktalk.net/MF-PV.htm
What do you say? Do I hear ‘coincidence, nonsense etc’, or do you have a more constructive opinion ?
vukcevic says:
December 19, 2010 at 6:13 am
you may consider obvious alternative, the gmf has control of stratospheric vortex.
What do you say? Do I hear ‘coincidence, nonsense etc’, or do you have a more constructive opinion ?
This is not an ‘obvious alternative’ as it also has to make sense energetically – and it doesn’t. The stratospheric vortex is controlled by upwards-traveling waves from the troposphere.
Carla says:
December 19, 2010 at 6:01 am
………
They use Mercator projection (up to 70N/S), where distortions are bearable. Polar projections also available:
http://www.vukcevic.talktalk.net/MF-PV.htm
Leif
If as you say that “The stratospheric vortex is controlled by upwards-traveling waves from the troposphere.”
What then is responsible for the regular increases in the temperature, geopotential heights and associated ozone anomalies in the polar stratosphere as seen here:http://www.cpc.noaa.gov/products/stratosphere/strat_a_f/
and here: http://www.cpc.ncep.noaa.gov/products/precip/CWlink/daily_ao_index/hgt.shtml
One observes that positive anomalies in ozone, temperature and geopotential heights appear when the Arctic oscillation (AO) index falls. i.e. when surface atmospheric pressure increases.
Are you saying that planetary waves are responsible for the fall in the AO (or the increase in surface atmospheric pressure that is part and parcel of the fall in the AO)?
I would be interested in your explanation of the physics behind that conjunction. Does a planetary wave cause a shift of the mass of the atmosphere towards the pole? Could the changing incidence of planetary waves be responsible for the 25mb fall in atmospheric pressure at the south pole between 1948 and 2010.
And what is a ‘Planetary wave’?
Leif Svalgaard says:
December 19, 2010 at 6:28 am
…………….
So you say Coriolis forces in troposphere are cause of this:
http://www.vukcevic.talktalk.net/MF-PV.htm
but the stratosphere is ionised.
erlhapp says:
December 19, 2010 at 7:54 am
And what is a ‘Planetary wave’?
All this is textbook stuff. Basic knowledge. Some pointers:
http://science.nasa.gov/science-news/science-at-nasa/2001/ast11oct_1/
http://en.wikipedia.org/wiki/Sudden_stratospheric_warming
http://www.atmos-chem-phys.org/10/707/2010/acp-10-707-2010.pdf
etc
vukcevic says:
December 19, 2010 at 8:12 am
but the stratosphere is ionised.
No, not anymore than my backyard.
vukcevic, I agree, and I don’t know.
I always wonder about the iron-nickel core breaking the magnetic lines of flux from the sun. That should cause electrons to flow and also heat because of resistance.
erlhapp says:
December 19, 2010 at 7:54 am
……………….
At the South Pole 1948 – 2010
The main field GMFf fell from 60592.6 to 55205.2 nT or 8.9%.
The vertical component GMFz fell from 58229.6 to 52635 nT or 10%.
This is partially due to fall in the Earth’s magnetic field, and partially to the drift of the magnetic pole towards Australia.
At location of the Australian base ‘Commonwealth Bay’ both GMFf and GMFz have equal values and both fell by 3.4 % .
If you can find pressure differential for the CB station that could be a starting point.
maelstrom the irreverent says:
December 19, 2010 at 8:59 am
I always wonder about the iron-nickel core breaking the magnetic lines of flux from the sun.
You can stop wondering [alway good to have less thing to wonder about, isn’t it?] because it doesn’t. The magnetic field [created in the core] can reconnect [40,000 miles away from the Earth] with the Sun’s magnetic field carried to us by the solar wind, and briefly allow the two fields to interact and electric currents to flow in the upper atmosphere.
Leif Svalgaard says:
December 19, 2010 at 8:58 am
No, not anymore than my backyard.
Than you could get some free electricity, by hanging couple of wires in your backyard.
Google Scholar will give you dozens studies on the subject of the stratospheric ionization.
vukcevic says:
December 19, 2010 at 9:05 am
At the South Pole 1948 – 2010
The main field GMFf fell from 60592.6 to 55205.2 nT or 8.9%.
And how much did the GMF fall there the past 2000 years? or since 1600?
vukcevic says:
December 19, 2010 at 9:24 am
Google Scholar will give you dozens studies on the subject of the stratospheric ionization.
And on ionization at the surface too. Please don’t pollute the blog with irrelevant stuff you don’t know much about. You can ask if you want to know something.
Re: “I used to work on Earth rotation, and remember when it wasa first suggested that distant quasars could be used as a precise indicator of irregularities in the Earth’s motion. Congratulations to the radio astronomers who devised this procedure, and to those who have used it to investigate the nature of the planet’s magnetic field.”
The decision to use quasars as some sort of standard candle is in truth a treacherous one, as the issue of where quasars are actually located, regardless of claims that there is nothing to see here, has been an issue of contentious debate for many years now.
If they are indeed at the distances which conventional theorists infer from their redshifts (near the edges of what we can see), then they exhibit meta-physical brightnesses.
Don’t forget that Halton Arp was relieved of his telescope time in his study of such objects, since he inferred that these objects could be plainly observed to be affiliated with more local galaxies. Bridge-like filaments, in some instances, can be observed in certain spectra connecting the quasars to their alleged host galaxies. When contradicting Arp’s claims, conventional publications have on occasion published that imagery which contains spectra which do not show the bridge. We all need to wonder why it is that they appear to be misleading people on the evidence?
Pairs of quasars with similar redshifts can be seen to align with the axes of certain energetic galaxies. Furthermore, the raw redshifts can be inferred to possess *quantized* inherent components. As these quasars age, they appear to take on additional mass, normalize their redshifts and reduce their brightness. One can logically argue that there exists a far less metaphysical inference that there are things happening here which actually illustrate unexpected linkages between mass and electrical charge. The quantization itself suggests some sort of small-scale process happening on a very large scale. To be clear, the set of inferences we’re seeing on this subject in print is definitely constrained by the Big Bang framework.
The jury is still out on this one, guys.
My understanding is that when continental drift theory was first put forth, it was assumed that land masses were floating above a liquid mantle. Now it is the more accepted theory, and one based on good seismic evidence, that continental drift is caused by subduction and abduction “creep”. It isn’t floating, it’s creeping and crawling around, loosing edge here and gaining it there at different rates.
Leif Svalgaard says:
December 19, 2010 at 9:38 am
Please don’t pollute the blog with irrelevant stuff you don’t know much about. You can ask if you want to know something.
You are often wrong as in this case of the stratosphere ionisation (and there is great deal of difference between stratosphere and the surface !).
When I don’t know something I do not ask (implies an answer from a person, whose competency can’t be guarantied), I read number of scientific articles on the subject. Google scholar is particular good search engine.
Rest of your comment I shall gladly disregard.
Chris Reeve says:
December 19, 2010 at 9:42 am
The jury is still out on this one, guys.
Not any longer, although you can always find die-hards.
Chris Reeve says:
December 19, 2010 at 9:42 am
If they are indeed at the distances which conventional theorists infer from their redshifts (near the edges of what we can see), then they exhibit meta-physical brightnesses.
They are indeed very bright, but not meta-physically so. There are good physical reasons for their brightness. That the quasars are very distant can be seen directly from the gravitational lensing by far-away galaxies: http://apod.nasa.gov/apod/ap060524.html
Chris Reeve says:
December 19, 2010 at 9:42 am
If they are indeed at the distances which conventional theorists infer from their redshifts (near the edges of what we can see), then they exhibit meta-physical brightnesses.
More on quasars at great distances:
http://imagine.gsfc.nasa.gov/docs/features/news/grav_lens.html
@Enneagram December 17, 2010 at 11:19 am:
Enneagram, When this says an “accelerator,” they mean an accelerometer. That is what I thought they meant, and that is what the link talked about.
I’ve worked a small bit with accelerometers (long ago), and normal accelerometers measure increasing or decreasing MOVEMENT. They don’t have to be measuring changes in the gravitational force. In fact, I doubt very seriously if that is what they are doing. My best understanding is that the ground started moving subtly before the quake, accelerating the building the accelerometer was mounted within. The accelerometer did what it is supposed to do – indicate that the building moved.
I mean, that is a good application for an accelerometer, if the one they used was sensitive enough, which it was. Thinking about it, I am a bit surprised no one has thought to use them for that before. In a practical sense. Geologists probably use them around volcanoes. If they have not used them for quakes before, I’d be shocked. But if they did, why would they be scratching their heads over how to predict quakes shortly before they happen? I REALLY don’t think many quakes happen without some motion just beforehand. Maybe I am wrong on that, though…
My point here is that I think these people are misunderstanding what the accelerometer indicates/measures.
Re: “They are indeed very bright, but not meta-physically so. There are good physical reasons for their brightness. That the quasars are very distant can be seen directly from the gravitational lensing by far-away galaxies: http://apod.nasa.gov/apod/ap060524.html”
You could have asked for an image of the bridge.
But, instead, you proposed an inference to explain an inference. And not only that, but gravitational lensing oftentimes lacks sufficient baryonic matter to mathematically work. So, to make it so, theorists will oftentimes sprinkle in some dark matter to glue the theory to the data.
This is not science, guys.
One would think that advocates for gravitational lensing would be producing sequences of imagery which demonstrate a lensing effect over time, but what we usually get instead is a single snapshot. Why is that?
This quote must unfortunately remain unattributed, but the sources are there for everybody to double-check …
“[T]here is strong reason to doubt that the ‘object at the very center of our galaxy’ is a black hole. According to gravitational astronomers, such a black hole should produce a gravitational lensing effect, particularly for the star S2 which is in orbit around Sagittarius A*. Time resolved images of a number of rapidly moving stars in this area have been available since 1992. See for example R. Schoedel et al, “A star in a 15.2 year orbit around the supermassive black hole at the centre of the Milky Way,” Nature 419 (2002), pp.694-696.
It is at this point that a presentation by E.H. Dowdye Jr. at the NPA conference in June assumes some significance. He noted that today’s observational tools should easily detect such lensing effects of a black hole of the size estimated from the above data. However, he points out in his paper [pp.131-136 of the NPA Conference Proceedings] that, even though this region has been under intense astrophysical observation since 1992, these observations have revealed “not a shred of evidence for any gravitational lensing.” The implication that necessarily follows is that the center of our galaxy does NOT contain any ‘black hole,’ otherwise the lensing would indeed occur.”
Upon what philosophical basis do conventional theorists and advocates ignore such problems?
Conventional thinkers will take down anybody who stands in the way of their preferred ideology. Halton Arp was one of the world’s most famous and respected astronomers when he presented observations which suggested that quasars are in fact associated with nearby energetic galaxies. He studied galaxies which were peculiar, and many of these galaxies are to this day named after him. He submitted his quasar paper for review to a black hole expert, Subrahmanyan Chandrasekhar, whose life work was threatened by this new observation.
Chandrasekhar in turn scribbled, “This is beyond my comprehension”, onto the paper and refused to send it off to an impartial referee. Over time, since Arp was not generating research which was considered important compared with his astronomical peers, he would eventually lose his telescope time here in the United States. He has since moved to Europe where he can continue it.
Most of these facts about Arp are by now well known to many, as they have been corroborated by people like Fred Hoyle and the Burbidges in “Universe — The Cosmology Quest”. One need only observe the YouTube or Google Video. Those who aren’t familiar with the details of the controversy might possibly ask themselves why it is so, and upon what philosophical basis they decide to ignore the controversy, and then propose that gravitational lensing can act as proof for anything at all. As for the public, they clearly expect that our theorists listen to our astronomers, and not dismiss their concerns when it suits the framework we taught them in college. Clearly, if Arp is right, then he has disproven the Big Bang theory. The road to truth in science is not a paved road, but you’d not know it talking to conventional theorists and advocates.
The dismissive response that Arp and others have received is completely inappropriate given the weight of the controversy, and the details of the debate.
Making matters worse, we can by now actually see the “black hole” at the center of our Milky Way galaxy in radio spectra, and it contains unexpected structure which conventional theorists never predicted. There is an image available here …
http://www.holoscience.com/news.php?article=7qqsr17q
The large majority of the imagery which people use to discuss NGC 7320 uses spectra which DO NOT SHOW THE CONNECTING BRIDGE. The bridge, however, can be observed plainly on Don Scott’s website at http://www.electric-cosmos.org/arp.htm, about halfway down the page.
Excerpt …
“In “Quasars, Redshifts, and Controversies” (p. 96-101) Halton Arp discusses the five interacting galaxies NGC 7317, 7318A, 7318B, 7319, and 7320 that constitute Stephan’s Quintet. The last one, NGC 7320, has a redshift value of 800 km/sec. The other four have redshifts of either 5700 km/sec or 6700 km/sec. Mainstream astronomers therefore claim those last four are about eight times farther away from us than NGC 7320. Therefore, they say, there cannot be any interaction between 7320 and the others.
Arp states “The deepest 200 inch (Mt. Palomar) plates that I have been able to obtain clearly show a ‘tail’ coming out of the southeast end of NGC 7320.” He points out, “A tail like this from NGC 7320… must be an interaction tail – which could arise only from physical interaction with the adjacent high-redshift members of the Quintet.”
He then states that at least one amateur has been able to see the tail but, “it is amazing that so many professionals have difficulty seeing it.” NASA routinely crops their images of Stephan’s Quintet to exclude the area where this tail would be seen.
However, my good friend, amateur astronomer John Smith acquired a full image of the Quintet.
The large, dark galaxy on the left is the low redshift NGC 7320. Then going counter-clockwise we have 7317, 7318A, 7318B, and 7319. At the top of the image is the small galaxy NGC 7320C. After some digital image processing (which only increased contrast), the result shown below was obtained.”
If, after all of that, you still possess some great confidence that redshift can be explained with only one single velocity-based inference, then you might want to consider that you’ve permitted yourself to become biased. To those of us who remain open minded on this controversy, it is plain to see that mainstreamers are choosing which evidence to pay attention to, and playing games with spectra to make their point.