Astrophysicists suggest solar flare could explain carbon-14 bump in AD 774

Nov 29, 2012 by Bob Yirka report
Comparison of Fusa Miyake's et al. data with a four-box carbon cycle simulation. Credit: Nature, 491, E1–E2 (29 November 2012) doi:10.1038/nature11695

(Phys.org)—Astrophysicists Adrian Melott and Brian Thomas of the University of Kansas and Washburn University respectively, have published a "brief communication arising" piece in the journal Nature suggesting that the conclusions of a team of Japanese researchers from Nagoya University regarding the source of a carbon-14 bump in AD 774-775 were in error. The Japanese team published an article earlier this year, also in Nature in which they suggested the brief bump in carbon-14 as evidenced by tree samples, was likely not the result of solar flares or a supernova.

In their paper, the team from Nagoya described their results in measuring the amount of carbon-14 in Japanese cedar that represented the years AD 750 to AD 820 with one and two year resolution. In so doing, they found a rapid, 12 percent increase in the amount of carbon-14, over the period AD 774-775, indicating that an extremely energetic event of unknown origin had occurred during that time period. They noted that the bump was approximately 20 times that seen from normal solar activity and for that reason ruled out a solar flare as a possible cause. They also ruled out a supernova as a likely source as it would have been seen and noted by people living at the time.

Carbon-14 is a variant of normal carbon-12 and tends to show up on planet Earth when cosmic particles strike the atmosphere producing showers of neutrons, which in turn strike causing a reaction that results in the creation of carbon-14. That carbon-14 then falls and in this case, abundant amounts landed on some cedar trees in Japan 1,238 years ago. The Japanese team suggest that if such a bump was due to a solar flare it would have had to have been thousands of times larger than any that has ever been recorded, making it an unlikely possibility.

Melott and Thomas disagree and write that it's possible a solar flare could have caused the bump if it shot out in blobs, rather than as a that spewed in all directions. If that were they case they say, a just 10 or 20 times the size of the largest ever recorded (the Carrington event of 1859) could very easily explain the carbon-14 bump during that time period.

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More information: Causes of an ad 774–775 14C increase, Nature, 491, E1–E2 (29 November 2012) doi:10.1038/nature11695

Abstract
Atmospheric 14C production is a potential window into the energy of solar proton and other cosmic ray events. It was previously concluded that 14C results from AD 774–775 would require solar events that were orders of magnitude greater than known past events. We find that the coronal mass ejection energy based on 14C production is much smaller than claimed in ref. 1, but still substantially larger than the maximum historical Carrington Event of 1859. Such an event would cause great damage to modern technology, and in view of recent confirmation of superflares on solar-type stars, this issue merits attention.

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User comments : 7

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philw1776
1 / 5 (3) Nov 29, 2012
We could lose huge % of the population were such a Carrington event occur today. Much more of a threat than the slow warming the press and climate scientists get vapors about.
antialias_physorg
5 / 5 (2) Nov 29, 2012
We could lose huge % of the population were such a Carrington event occur today.

Why? We didn't lose a single person when the Carrington event occured in 1859. What's so different/more susceptible about people alive today?
eachus
3 / 5 (2) Nov 29, 2012
Why? We didn't lose a single person when the Carrington event occured in 1859. What's so different/more susceptible about people alive today?


There are thousands to millions of people in potentially hazardous situations that didn't exist in 1859. Automobile fatalities are much more likely to be caused by failure of signalling systems than on-board electronics failures, same for trains, but aircraft and spacecraft will be susceptible to both failure modes.

Hmmm. Total number of people in 1859 in planes, automobiles and spacecraft? Zero. (There were failures of telegraph systems associated with railroads.)

Failures of weather satellites could allow storms like Sandy to escape detection until less than 24 hours before (coastal) impact. Others at risk include those in hospitals connected (electrically) to external equipment, and people with implanted electronics (usually pacemakers). Again not many weather satellites in 1859 and no electronics of any type.
antialias_physorg
5 / 5 (4) Nov 29, 2012
Automobile fatalities are much more likely to be caused by failure of signalling systems than on-board electronics failures

It' not like these happen every day somwhere. And somehow I get the impression of a definite lack of mass collisions in the news.

Total number of people in 1859 in planes, automobiles and spacecraft?

Total number of people in spacecraft when this happens? Zero
Total number of people in airplanes when something like this happens: Zero

Why? because we are able to look at the sun and see something like this happening way before it hits us.

Failures of weather satellites could allow storms like Sandy to escape detection until less than 24 hours before (coastal) impact.

We do have other means of observing the weather. There are such things as ships out at sea. Hurricanes don't develop out of nowhere in an instant.
cantdrive85
2 / 5 (4) Nov 29, 2012
A Carrington type event could render the "grid" inoperable for quite a long period of time. A large enough CME could behave like an EMP device and fry electronics on a global scale. Being that nearly everything (econ, food production, energy, etc...) has become computerized or electronically based, it's not a reach to say this would be catastrophic. Imagine the hardship if even 30% of the electronic systems worldwide failed. Imagine the hardship if the power supply didn't get restored for 6-12 months. In this situation, people in less developed countries that rely more on human effort, low tech, and ingenuity will be better off than say those in the US that depend so heavily on technology for our daily needs.
FainAvis
5 / 5 (4) Nov 29, 2012
Confusion in article:
"...showers of neutrons, which in turn strike hydrogen nuclei causing a reaction that results in the creation of carbon-14."

From wikipedia:
"Carbon-14 is produced in the upper layers of the troposphere and the stratosphere by thermal neutrons absorbed by nitrogen atoms. When cosmic rays enter the atmosphere, they undergo various transformations, including the production of neutrons. The resulting neutrons (1n) participate in the following reaction:

1n + 14N → 14C + 1p "

Reporter has mixed up hydrogen and nitrogen.
yyz
not rated yet Dec 03, 2012
A preprint of the Melott and Thomas paper in Nature has been posted here: http://arxiv.org/abs/1212.0490