From the AGU weekly highlights:
Large solar proton event explains 774-775 CE carbon-14 increase
Tree ring records indicate that in 774-775 CE, atmospheric carbon-14 levels increased substantially. Researchers suggest that a solar proton event may have been the cause. In solar proton events, large numbers of high-energy protons are emitted from the Sun, along with other particles. If these particles reach Earth’s atmosphere, they ionize the atmosphere and induce nuclear reactions that produce higher levels of carbon-14; the particles also cause chemical reactions that result in depletion of ozone in the ozone layer, allowing harmful ultraviolet radiation to reach the ground.
A previous group of researchers suggested that to cause the observed eighth century carbon-14 increase, a solar proton event would have had to be thousands of times larger than any that has been observed from the Sun. However, Thomas et al. believe that group’s calculations were incorrect. They modeled the atmospheric and biologic effects of three solar proton events with different energy spectra and fluences (number of protons per area). They find that an event with about 7 or more times greater fluence (depending on the spectrum) than an observed October 1989 solar flare event could explain the 774-775 CE carbon-14 enhancement. With a hard (high-energy) spectrum, an event with this fluence would result in moderately damaging effects on life but would not cause a mass extinction. They rule out an event with a softer spectrum because such an event would cause severe ozone depletion and mass extinction, which were not observed in the eighth century. The authors estimate that solar proton events of this magnitude occur on average once in a thousand years, and more often if the estimate is based on astronomical observations of flares on Sun-like stars. They note that although that may seem low, such an event would have severely damaging effects on the technology on which society relies.
Source:
Geophysical Research Letters, doi:10.1002/grl.50222, 2013 http://onlinelibrary.wiley.com/doi/10.1002/grl.50222/abstract
Title:
Terrestrial effects of possible astrophysical sources of an AD 774-775 increase in carbon-14 production
Abstract:
We examine possible sources of a substantial increase in tree ring14C measurements for the years AD 774-775. Contrary to claims regarding a coronal mass ejection (CME), the required CME energy is not several orders of magnitude greater than known solar events. We consider solar proton events (SPEs) with three different fluences and two different spectra. The data may be explained byan event with fluenceabout one order of magnitude beyond the October 1989 SPE.Two hard spectrum cases considered here result in moderate ozone depletion, so no mass extinction is implied, though we do predict increases in erythema and damage to plants from enhanced solar UV.We are able to rule out an event with a very soft spectrum that causes severe ozone depletion and subsequent biological impacts.Nitrate enhancements are consistent with their apparent absence in ice core data. The modern technological implications of such an eventmay beextreme, and considering recent confirmation of superflares on solar-type stars, this issue merits attention.
Authors:
Brian C. Thomas, Keith R. Arkenberg and Brock R. Snyder II: Department of Physics and Astronomy, Washburn University, Topeka, Kansas, United States;
Adrian L. Melott: Department of Physics and Astronomy, University of Kansas, Lawrence, Kansas, United States.
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Mike says:
March 15, 2013 at 9:20 pm
If one could touch the surface of the sun what would the density feel like?
It would be more than a thousand times thinner than the air we breathe; something like the air at an altitude of 50 km, thus a pretty good vacuum.
Also, what is the density/pressure at the core believed to be?
The density is about 150 times the density of water or 13 times denser than Lead or more than 100,000 times that of air at the ground. The pressure is enormous: about 300 billion times the pressure of the Earth’s atmosphere at its surface.
Thank you
lsvalgaard says:
March 15, 2013 at 7:14 pm
There is some agreement that waves of various kinds heat the corona, much as when you crack a whip. An important point is that the material gets thinner and thinner and so the same energy has larger and larger effect.
Waves back at you Dr. S.
A Major Step Forward in Explaining the Ribbon in Space Discovered by NASA’s IBEX Mission
02.05.13
..Indeed, since the discovery of the ribbon, over a dozen competing theories seeking to explain the phenomenon have been put forth. The new theory builds on one that was first published along with the discovery of the ribbon in 2009 and then quantitatively simulated in 2010. This theory posited that the ribbon exists in a special location where neutral hydrogen atoms from the solar wind cross the local galactic magnetic field. Neutral atoms are not affected by magnetic fields, but when their electrons get stripped away they become charged ions and begin to gyrate rapidly around magnetic field lines. This process frequently aims ions back toward the sun. So those ions that pick up electrons at the right time might explain the extra boost of neutral atoms that create the ribbon. The problems were that physical processes might break down the distribution needed for it to work and that models based on this process showed a ribbon narrower than IBEX observed.
The new theory adds a key process: That rapid rotation creates waves or vibrations in the magnetic field, and the charged ions then become physically trapped in a region by these waves, which in turn would amplify the ion density and produce the broader ribbon seen.
“Think of the ribbon as a harbor and the solar wind particles it contains as boats,” says Nathan Schwadron, the first author on the paper and scientist at The University of New Hampshire, Durham. “The boats can be trapped in the harbor if the ocean waves outside it are powerful enough. This is the nature of the new ribbon model. The ribbon is a region where particles, originally from the solar wind, become trapped or retained due to intense waves and vibrations in the magnetic field.”
Models done with these waves taken into account agree with the available observations, and the mathematical modeling results look remarkably like what the ribbon actually looks like, says Schwadron..
http://www.nasa.gov/mission_pages/ibex/news/ribbon-explained.html
Thank you for your replies Dr. S..
You’re a gem. Keep on shinin’ on!!
@ur momisugly George e. smith “””””…..You also have to have that happen a whole lot of times for the reactions to take place (often enough). So that requires high pressures at the same time as high Temperatures. Last time I heard, the coronal regions of the sun, were closer to a vaccuum than to anything very dense…….”””””
And waking up after reading Dr S, I realize that what is rquired is high density and high Temperature; the high pressure is simply a means to get that high density from gravitation,but the high density is what gives you lots of collsions, at high enough energies due to the Temperature.
Words have meaning; we really do need to use the right words.
And of course we do know that earth’s atmosphere at high enough altitudes, also gets much hotter than at lower altitudes, although probably for different reasons from the solar corona heating.
lsvalgaard says:
March 15, 2013 at 7:15 am
==========================
ok, but the ‘solution’ doesn’t match the evidence…physicist should stop checking since the model has been established so well?
“recent discovery that the Sun contains about half as much oxygen as previously thought, an issue some scientists have dubbed the solar oxygen crisis
Read more at: http://phys.org/news97326842.html#jCp”
http://phys.org/news97326842.html
Where are all the neutrinos hiding?
http://www.cora.nwra.com/~werne/eos/text/neutrino.html
http://www.physics.uc.edu/~sitko/Astrophysics-II/21-SSM.pdf
Kajajuk says:
March 16, 2013 at 11:37 am
ok, but the ‘solution’ doesn’t match the evidence…physicist should stop checking since the model has been established so well?
We do not stop checking. But you apparently stop looking for newer evidence. Both of those ‘problems’ have been resolved, by more recent data. The Oxygen problem has been partly resolved by refining the abundances of Neon and other elements as they all contribute to the opacity. The Neutrino problem has been solved by the discovery of neutrino oscillations using data from man-made neutrinos from reactors on the Earth. Discrepancies are where we learn to refine our models. Your comment [sadly] says more about your anti-science attitude than about the science.
Nice touch with the dig…Leif, you are clearly in a class of your own.
No reference for the solutions to the solution or is attitude sadly enough.
You must be quite the professor to the questioning student or at least label-or.
Kajajuk says:
March 16, 2013 at 6:22 pm
No reference for the solutions to the solution or is attitude sadly enough.
Your problem is not knowledge [or lack there of], but, as I said, ‘attitude’.
Your own reference http://www.physics.uc.edu/~sitko/Astrophysics-II/21-SSM.pdf
says: “The THREE Solar Neutrino Problems:
There were actually 3 solar neutrino problems now solved!”
No need for me to provide you with further, is there? You found it on your own [you just had to look].
“Quantitatively, the disagreement is less severe because the new abundances have slightly higher CNO abundances and a somewhat larger Ne abundance. The changes, however, do not help much neither in restoring the agreement with helioseismology nor in facilitating the way for alternative solutions in the form of modi- fied input physics for solar models. We have described with some detail the effect of the new composition in opacities and the required change to recover good helio- seismic properties. Changes of order 15% are needed, which are still much higher than currently estimated uncertainties in radiative opacities for the solar interior.”
http://arxiv.org/pdf/0910.3690v1.pdf
Exploring models with the Standard Solar Model “done” is curious to this anti-science observer. And so my attitude persists, that the Sun is not solved, as my anti-arrogance continues to wonder…
Kajajuk says:
March 16, 2013 at 7:06 pm
Exploring models with the Standard Solar Model “done” is curious to this anti-science observer. And so my attitude persists, that the Sun is not solved, as my anti-arrogance continues to wonder…
You just look for confirmation of your bias by citing older papers. The Oxygen abundance [as most of them] are deduced from modelling the line formation in the solar photosphere. Old models were 1D LTE models. The most recent calculations [e.g. http://www.leif.org/EOS/1302-1048-Oxygen-Abundance.pdf ]with a full 3D non-LTE model resolve most of the discrepancies. It seems we need to adjust several other abundances too. This is fine as we learn from discrepancies. Your assertion was that solar physicists don’t look anymore and that is clearly wrong. You can stop wondering and rest assured that problems are being attacked vigorously and not swept under the rug as you insinuate. The question is not is the ‘Sun is solved’ [it will never be – as the solutions can always be improved], but if it is solved well enough that we can have confidence in what we infer and conclude.
My sarcasm was not an assertion.
Lief,
The article i last cited was of 2009, solar physics must be cutting edge if that is an old work.
Your link comes up ‘404’; file not found.
Kajajuk says:
March 16, 2013 at 7:44 pm
My sarcasm was not an assertion.
Sarcasm is even worse than just being wrong. It has no place in a reasonable debate.
Kajajuk says:
March 16, 2013 at 7:50 pm
The article i last cited was of 2009, solar physics must be cutting edge if that is an old work.
This particular subject is under intense scrutiny and progress is swift. 404 is fixed if you would care to look. The point is that physicists NEVER stop looking. And that the problems you initially saw or imagined HAVE been solved or are being vigorously investigated.
anti-science, unreasonable debater, and unwarranted skeptic…well, thanks for helping with the physics (no sarc here) and helping with my personal evolution (sarc).
Kajajuk says:
March 16, 2013 at 8:18 pm
anti-science, unreasonable debater, and unwarranted skeptic…well, thanks for helping with the physics (no sarc here)
You see, the solar Neon abundance is very uncertain because Neon cannot be measured spectroscopically in the solar photosphere, but has to be inferred from other stars. Even back in 2005 this was clearly a problem, but with a solution:
E.g. Nature 436, 525-528 (28 July 2005) ‘The ‘solar model problem’ solved by the abundance of neon in nearby stars’ by Jeremy J. Drake & Paola Testa:
“The interior structure of the Sun can be studied with great accuracy using observations of its oscillations, similar to seismology of the Earth. Precise agreement between helioseismological measurements and predictions of theoretical solar models1 has been a triumph of modern astrophysics. A recent downward revision by 25–35 per cent of the solar abundances of light elements such as C, N, O and Ne (ref. 2) has, however, broken this accordance: models adopting the new abundances incorrectly predict the depth of the convection zone, the depth profiles of sound speed and density, and the helium abundance. The discrepancies are far beyond the uncertainties in either the data or the model predictions. Here we report neon-to-oxygen ratios measured in a sample of nearby solar-like stars, using their X-ray spectra. The abundance ratios are all very similar and substantially larger than the recently revised solar value. The neon abundance in the Sun is quite poorly determined. If the Ne/O abundance in these stars is adopted for the Sun, the models are brought back into agreement with helioseismology measurements”
Sometimes it helps to listen to people who know what they are talking about.
and helping with my personal evolution (sarc).
You personal evolution and attitude I cannot help with, so no sarc needed [as it does not belong in reasonable discussion between gentlemen]
Lief,
The point was missed; name calling in a discussion is childish and of little consequence, unless the intent is to insult…hence the sarc. Your labels of my character are meaningless and your personal attacks silly. Perhaps your anti-science is showing as is the ego on your sleeve.
A tangent for the experts:
“Trust me I know”
Kajajuk says:
March 16, 2013 at 9:11 pm
The point was missed
So you missed the point. Well, I have tried to explain the physics to you and you respond with sarcasm. That says it all, don’t you think?
Kajajuk says:
March 16, 2013 at 9:24 pm
“Trust me I know”
If you don’t know anything, everything is possible, and every solution is valid. Is this what the science illiterate public has sunk to?
lsvalgaard says:
March 16, 2013 at 9:25 pm
========================
I initiated a discussion related to the unsolved Sun and was told that i was anti-science, an unreasonable debater, and an unwarranted skeptic as well that, “Sometimes it helps to listen to people who know what they are talking about.”
And that i do think says it all.
Kajajuk says:
March 16, 2013 at 9:33 pm
I initiated a discussion related to the unsolved Sun and was told that i was anti-science, an unreasonable debater, and an unwarranted skeptic…
You asserted that “physicist should stop checking since the model has been established so well”. That was your sin, plus the not-called-for sarcasm.
Funny that the “assertion” was punctuated as a question => sarcasm.
That was the “not-called for sarcasm”, all other dastardly sarcasm was a direct result of personal attacks…let’s review professor…(paraphrased; hope your wit can deal)
kjjk: “Sun is not solved” and a non Standard Solar Model (SSM) alluded too. Viz: http://www.thunderbolts.info/tpod/2006/arch06/060120solar1.htm
(just for fun with the Sun, hehehe)
ls: oh yes it is!
kjjk: sarc question (boo hoo hooo), What about the Oxygen Crisis and the Neutrino Problem
ls: Those irritations have been solved, the SSM still rules, you anti-science moron
kjjk: sarc response to anti-science dig and subtle counter ‘attitude’ dig
ls: “Your problem is not knowledge [or lack there of], but, as I said, ‘attitude’.” Neutrino problem solved by modification of the Standard Model of particle physics, Neutrino Oscillations (aside…where does the differences in mass go, or come from, when neutrinos are oscillating between electron, muon, and tau?)
kjjk: quote from a 2009 paper that admits problems in the SSM and explores three models and a subtle arrogance dig at Lief
ls: “Trust me I know”
kjjk: the admission that the question was not an assertion but sarcasm
kjjk: 3 year old paper is old and link no good
ls: “Sarcasm is even worse than just being wrong. It has no place in a reasonable debate.”
ls: link fixed if you care to look (i did, thx); “The point is that physicists NEVER stop looking. And that the problems you initially saw or imagined HAVE been solved or are being vigorously investigated.” or paraphrased…Trust me I know!
kjjk: Thanks for the physics…Lief is a bully.
ls: Science explanations (thx again), “Sometimes it helps to listen to people who know what they are talking about.”…paraphrased “Trust me I know” and restated dig plus kjjk is not a gentlemen
kjjk: It is not nice to personally attack someone during a discussion.
ls: yes it IS, don’t you think? (no i do not think i leave it up to the experts ((sarc)))
ls: “If you don’t know anything, everything is possible, and every solution is valid. Is this what the science illiterate public has sunk to?” (oh ouchy)
kjjk: It is not nice to personally attack someone during a discussion.
ls: Yes it IS! and Lief hates sarcasm unless it is called for.
WTF
PS “Last word Lief” => this is not the last word…
Leif,
Though we may not have good data on the probability of a large flare occurance, since the event and the direction in which it is “aimed” are independent, the probabilies are still multiplicative. Therefore if one can make an estimate of liklihood of the event based upon observations of sun-like stars, then using your 30 degree window, .0833 x (the estimated probability of occurance)= the probability of a destructive result here, ie .001 x .0833=.0000833 if the probability of the event is one in 1000 in say a 100 year time frame or approximately 1 in 10,000 at any given time. Better some ranges of probabilities than nothing. And how do such estimates fit with geological evidence per the article? What does the geological evidence say about the historical freqency of impacts of such events here? How does it compare to observations of sun-like stars? Some various ways to look at the situation.