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Patterns in Earth's Magnetic Field Morph Every 1000 Years --"The Reason is a Mystery"


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Some 800,000 years ago, a magnetic compass' needle would have pointed south because the Earth's magnetic field was reversed. These reversals typically happen every several hundred thousand years. The geomagnetic field is critical to life on Earth. Without it, charged particles from the sun (the "solar wind") would blow away the atmosphere, scientists say. The field also aids in human navigation and animal migrations in ways scientists are only beginning to understand. Centuries of human observation, as well as the geologic record, show our field changes dramatically in its strength and structure over time.

Scientists have identified patterns in the Earth's magnetic field that evolve on the order of 1,000 years, providing new insight into how the field works and adding a measure of predictability to changes in the field not previously known.

The discovery also will allow researchers to study the planet's past with finer resolution by using this geomagnetic "fingerprint" to compare sediment cores taken from the Atlantic and Pacific oceans. Results of the research, which was supported by the National Science Foundation, were recently published in Earth and Planetary Science Letters.

Yet in spite of its importance, many questions remain unanswered about why and how these changes occur. The simplest form of magnetic field comes from a dipole: a pair of equally and oppositely charged poles, like a bar magnet.

"We've known for some time that the Earth is not a perfect dipole, and we can see these imperfections in the historical record," said Maureen "Mo" Walczak, a post-doctoral researcher at Oregon State University and lead author on the study. "We are finding that non-dipolar structures are not evanescent, unpredictable things. They are very long-lived, recurring over 10,000 years - persistent in their location throughout the Holocene.

"This is something of a Holy Grail discovery," she added, "though it is not perfect. It is an important first step in better understanding the magnetic field, and synchronizing sediment core data at a finer scale."

While scientists are well aware of the pattern of reversals in the Earth's magnetic field, a secondary pattern of geomagnetic "wobble" within periods of stable polarity, known as paleomagnetic secular variation, or PSV, may be a key to understanding why some geomagnetic changes occur.

The Earth's magnetic field does not align perfectly with the axis of rotation, which is why "true north" differs from "magnetic north," the researchers say. In the Northern Hemisphere this disparity in the modern field is apparently driven by regions of high geomagnetic intensity that are centered beneath North America and Asia.

"What we have not known is whether this snapshot has any longer-term meaning - and what we have found out is that it does," said Joseph Stoner, an Oregon State University paleomagnetic specialist and co-author on the study.

When the magnetic field is stronger beneath North America, or in the "North American Mode," it drives steep inclinations and high intensities in the North Pacific, and low intensities in Europe with westward declinations in the North Atlantic. This is more consistent with the historical record.

The alternate "European mode" is in some ways the opposite, with shallow inclination and low intensity in North Pacific, and eastward declinations in the North Atlantic and high intensities in Europe.

"As it turns out, the magnetic field is somewhat less complicated than we thought," Stoner said. "It is a fairly simple oscillation that appears to result from geomagnetic intensity variations at just a few recurrent locations with large spatial impacts. We're not yet sure what drives this variation, though it is likely a combination of factors including convection of the outer core that may be biased in configuration by the lowermost mantle."

The researchers were able to identify the pattern by studying two high-resolution sediment cores from the Gulf of Alaska that allowed them to develop a 17,400-year reconstruction of the PSV in that region. They then compared those records with sediment cores from other sites in the Pacific Ocean to capture a magnetic fingerprint, which is based on the orientation of the magnetite in the sediment, which acts as a magnetic recorder of the past.

The common magnetic signal found in the cores now covers an area spanning from Alaska to Oregon, and over to Hawaii.

"Magnetic alignment of distant environmental reconstructions using reversals in the paleomagnetic record provides insights into the past on a scale of hundreds of thousands of years," Walczak said. "Development of the coherent PSV stratigraphy will let us look at the record on a scale possibly as short as a few centuries, compare events between ocean basins, and really get down to the nitty-gritty of how climate anomalies are propagated around the planet on a scale relevant to human society."

The magnetic field is generated within the Earth by a fluid outer core of iron, nickel and other metals that creates electric currents, which in turn produce magnetic fields. The magnetic field is strong enough to shield the Earth from solar winds and cosmic radiation. The fact that it changes is well known; the reasons why have remained a mystery.

Now this mystery may be a little closer to being solved.

The Daily Galaxy via Oregon State University

Image credit: With thanks to BBC 

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Comments

Wow are you serious with this article? I mean "Patterns in Earth's Magnetic Field Morph Every 1000 Years --'The Reason is a Mystery'" is not even close to being correct. I can give you the reason right now and it actually is very very simple and it took me less time to figure it out than it did to read less than half that article.

I can tell you with 100% certainty that the moon is moving away from us and as it does the core of the earth cools just a little more and there is a little less rotation inside the core as a result, thus leading to our field changes dramatically in its strength and structure over time(sic).

Now seriously I could go into more detail as to why, but I am not. I am not an astronomer or a geologist, yet for some reason those people cant put 2 and 2 together. The astronomer does not seem to understand the geology of the situation and the geologist does not seem to understand what is causing this to happen because nothing 'on' this earth can explain it.

Seriously people are you telling me that we have the best minds working on this? It took me all of 5 minutes to get it, what is their problem?????

Bil - Not particularly caring for using ad hominem arguments to dispute study and experimentation, I looked up where the earth’s mantle gets its heat to stay liquid-ish. The answers were accretion, falling iron friction and uranium/thorium decay. None of these involve Luna.

Surprising to me was that accretion represented the largest heat source - that the heat generated by original formation of rocks grinding together, forming into a ball and getting hit by asteroids, was and is still retained after some 4 billion years. Little of that heat has been radiated away because the earth’s crust – 3-5 miles under the sea and 25 miles under the continents - is a damned good heat blanket.

My question of this article is: would it not be possible to “observe” when the N-S poles went to S-N with not only a magnetite layer change but with a die off too. What I was told in school is that we are pretty well protected from killer radiation with our strong magnetosphere. But on reversal (which I assume didn’t just happen overnight) wouldn’t we be unprotected and some species suffer for it?

Deryl, do you realize just how much of this falling iron friction and uranium/thorium decay it would take to heat the entire core to the temperature that it is? The inner core is iron nickel last I heard, even though that is just a guess, it is not a uranium/thorium core. I mean think about it, all of this uranium would have to be in one spot in order to produce enough heat and that would have to be a very big spot, and if the core is moving then the chances of it being all together are very slim. There would have to be so much uranium in order to keep it hot enough for there to be volcanoes and hot springs and the like, in fact Hawaii and Iceland should be highly irradiated, not to mention Yellowstone and various other hot springs, geysers, volcanoes, and underwater thermal vents. Yet I have never heard of someone getting radiation poisoning from Yellowstone or being in Hawaii. Its just common sense man.imagine that the oceans were quite a bit thicker, but not solid. And the tidal pull was the same as it is now. Just how hot do you think that would be?

Now as far as your second comment, " that the heat generated by original formation of rocks grinding together" I will just give you one word and let you figure it out, infact this word should be enough explanation for both of the comments. That word is Mars.

Well as far as the N/S switch it does not happen over night as you said but gradually and that would mean that the poles drift from one point to another over time. Now since there are holes at the poles in the magnetosphere, then yes there will be damage done, imagine being at the poles where the holes are biggest. There will be more cases of skin cancer and things of that sort, assuming that humans do not evolve to a point where it will not lead to cancer. I really do nothing that there will be a big die off or anything. Besides with people like trump and kim jong-un humans only have a few more years..

"Now seriously I could go into more detail as to why, ..."

No, please, Bill. I insist. Go into more detail and enlighten us and the experts.

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Freddy if you are so smart then please let us know why Venus and mars have not magnetosphere? Why does mars no longer have any active volcanoes and have not had any for several billion years? If the theory about " that the heat generated by original formation of rocks grinding together" then mars should still have volcanic activity, because Earth sure does. Put 2 and 2 together and try to get 4. It is a pretty simple concept.

Venus doesn't have a magnetosphere because it rotates too slowly.
There's also (fairly recent) evidence to suggest that Mars does have active volcanic activity.

The radiation is trapped within the mantle by several hundred miles of molten iron and nickel. Also any radioactive elements that reach the molten core would sink gravitationally to the center.

Sometime I am suspecting that the Sun's particle radiation charge and Sun magnetoactivity is the cause for the magnetic fields switch.

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