Rice researcher part of team that used Doppler shifts to ID phenomenon; may help predict space weather
Left, image of hot (1.8-million degree Fahrenheit) active region loops. Right, flows of solar plasma (blue shifts). Credit: Left: SDO/AIA (NASA); right: Hinode/EIS (JAXA, NASA, ESA and STFC)
A Rice University astrophysicist is part of an international team that combined Doppler techniques with images and data from a space-based telescope to observe, for the first time, loops of 1,800,000-degree Fahrenheit plasma flowing up from the sun’s surface at more than 12 miles per second.
The loops, rooted in active regions near sunspots and guided by the sun’s magnetic field, arch over the sun and may be the first signs of trouble spots, where plasma undergoes “impulsive heating,” according to the researchers. They expect their findings will help scientists understand the genesis of solar flares and coronal mass ejections – solar storms – that threaten satellites orbiting Earth and power transmission grids on the ground.
Rice’s Stephen Bradshaw and colleagues in India and the United Kingdom reported their results today in the Astrophysical Journal Letters.
They wrote that Doppler measurements drawn from images taken by the Extreme-ultraviolet Imaging Spectrometer (EIS) aboard the Hinode solar satellite show the first observation of a “warm loop” in which plasma rises from the surface of the sun rather than sinks back into it.
In visible-light Doppler, objects moving away from the viewer are shifted red, while objects moving closer shift blue. That fact has long been useful to astrophysicists judging how fast other stars and even galaxies are moving in an expanding universe. But in previous observations of active regions on the sun, warm loops like the one observed by Bradshaw and his colleagues have only been seen to shift red and, therefore, the plasma was thought to be sinking.
The prevalence of red shifts led to the belief that heating is taking place high in the sun’s atmosphere and leading to the evaporation of material from near the surface into the atmosphere that then flows back down as it cools. That may be true, Bradshaw said, but it leaves some important questions unanswered: What causes the heating? Where is the evidence for plasma rising from the surface into the atmosphere?
The new observations will help to answer these questions, he said.
“The blue shifts are the signature, or ‘smoking gun,’ of plasma flowing up into the atmosphere,” said Bradshaw, Rice’s William V. Vietti Junior Chair of Space Physics and an assistant professor of physics and astronomy. “They show that the fastest up-flows are found near the surface of the sun. This information gives us clues to the location where the heating is taking place, how fast it is and how much energy is needed.”
“The sun governs the environment in which we live, and it is the so-called solar active regions that drive extreme conditions leading to the explosive flares and the huge eruptions; understanding these active regions is absolutely critical for the study of what we now call space weather,” said Richard Harrison, head of space physics and chief scientist at the Rutherford Appleton Laboratory in the United Kingdom. “The work published in this paper is a key element of that work, applying innovative analyses to the observations from the U.K.-led Hinode/EIS instrument.”
Bradshaw noted the sun is fast approaching the part of its 11-year cycle when flares and coronal mass ejections occur most frequently. “These events present the most danger to satellites, power grids and even to airliners on flight paths in polar regions,” Bradshaw said. “This period is called solar maximum, and we will become ever more reliant on this technology during every subsequent solar cycle.
“One of the aims of solar research is to develop a space-weather forecasting capability, whereby solar storms can be predicted by detecting their signatures before they occur at the sun,” he said. “This is much like monitoring depressions as precursors to tropical storms and hurricanes, but space-weather forecasters will monitor active regions. Accurate forecasts of solar storms will give us the maximum possible time to prepare for their arrival at Earth and to mitigate their effects.
“Our work will contribute to this aim by leading to a better understanding of the physics of active regions.”
Co-authors are principal investigator Durgesh Tripathi ofthe Inter-University Centre for Astronomy and Astrophysics in Ganeshkhind, India; and Helen Mason, assistant director of research, and Giulio Del Zanna, an advanced fellow in the atomic astrophysics group, both in the Department of Applied Mathematics and Theoretical Physics at the University of Cambridge.
The Hinode satellite was launched in 2006 by the of Space and Astronautical Science and the Japan Aerospace Exploration Agency, in collaboration with the National Astronomical Observatory of Japan, NASA and the and Technology Facilities Council the United Kingdom. The European Space Agency and Norwegian Space Centre also supported the research.
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Read the abstract at http://iopscience.iop.org/2041-8205/754/1/L4
So which of these chaps gets the credit for figuring out the temperature in deg F ?
Why didn’t they just say the temperature was 999,982.222 deg C, or even 1,000,255’372 K ?
for the first time
some of the usual [over]hype. Rising loops have been observed for a long time. Here is ‘Grandpa’ from 1946: http://www.leif.org/research/Grandpa-1946.png
“When a gust of solar wind hits Earth’s magnetic field, the impact causes the magnetic field to shake. If it shakes hard enough, we call it a geomagnetic storm.” In the extreme, these storms cause power outages and make compass needles swing in the wrong direction. Auroras are a beautiful side-effect.”
“The amount of geomagnetic activity now tells us what the solar cycle is going to be like 6 to 8 years in the future,” says Hathaway. A picture is worth a thousand words:
http://science.nasa.gov/science-news/science-at-nasa/2006/21dec_cycle24/
It is questionable to assume that the Earth bound GEO-magnetic indices have nothing to do with the rapid changes in the Earth’s magnetic field caused by changes in the Earth’s core angular momentum changes (here differential)
http://www.vukcevic.talktalk.net/Aa-CAM.htm
Note 7 years advance in Aa to the CAM’s change
NASA: Cross correlating sunspot number vs. IHV, they found that the IHV predicts the amplitude of the solar cycle 6-plus years in advance with a 94% correlation coefficient.
http://science.nasa.gov/media/medialibrary/2006/12/21/21dec_cycle24_resources/hathaway1_strip2.jpg
Do solar scientists need to re-examine their theories a bit more closely?
May be over my head but, if there is a loop of plasma sticking out of the surface, then obviously one half of it has come up and the other half is going down. Have watched videos showing this looping so dont understand why they say they havent seen this before without doppler? Or am i being obtuse?
the good news will come soon that the sun controls our weather not Al Gore and his disciples
Here is an interesting alternative theory.
http://www.thunderbolts.info/tpod/2010/arch10/100921circuits.htm
vukcevic says:
July 5, 2012 at 12:26 am
It is questionable to assume that the Earth bound GEO-magnetic indices have nothing to do with the rapid changes in the Earth’s magnetic field caused by changes in the Earth’s core angular momentum changes
You are still pushing your nonsense.
vukcevic says:
July 5, 2012 at 12:26 am
NASA: Cross correlating sunspot number vs. IHV, they found that the IHV predicts the amplitude of the solar cycle 6-plus years in advance with a 94% correlation coefficient….
Do solar scientists need to re-examine their theories a bit more closely?
It clearly failed on cycle 24, so perhaps Hathaway [not NASA] should do that [and he has]. You shouldn’t spread this misleading stuff, either.
AJ says:
July 5, 2012 at 5:17 am
Here is an interesting alternative theory.
Entertaining, but dead wrong. You can see here http://dealingwithcreationisminastronomy.blogspot.com/p/challenges-for-electric-universe.html why.
@vuk
“Do solar scientists need to re-examine their theories a bit more closely?”
Well, if a solar scientist was doing their job, that would be a continuous process, with or without challenges from the peanut gallery.
It was interesting to note that the link Leif provided is called ‘creationism in astronomy’ as a way of making it appear that any theory that does not match the mainstream/consensus view is equivalent to a ‘creationist view’ of the universe. That is the sort of argument that screams, “I don’t have any other decent rebuttal!” Jeez. I thought we had enough of that with ‘denier’ discussion: guilt by faulty faith in the wrong Faith.
Leif, I read all your posts here and check many of your references. I have observed that you are completely conventional in your approach to all matters of the sun (standard model and all that) except when it comes to those narrow topics in which you are innovating. You demand that everyone accept the conventional views of how the sun works, except those things you are investigating where ‘something new’ is being explored that does not already form part of the standard solar model. I have a problem, not with you, but with that approach to the arguments of others. The standard solar model contains many assumptions and guestimates. Coronal heating is one of the mysteries and there are unconventional views as to what might be causing it.
If you are capable of finding out something new about the sun that edits or shifts the standard model, why should others not make similar investigations? This article about doppler shift being used to trace the point at which heating has taken place is very interesting. There may have been a ‘standard guess’ but being popular is not ‘truth’. The result of the work above does not explain the heating, yet. The fact is, coronal heating exactly matches the profile of a plasma current.
I find it irritating that you harass Vuk so much, day in, day out, about his wide ranging exploration of correlations many of which I find fascinating and which point to possible alternative relationships that do not match the standard model. So what? There are so many unkowns to be bothered trying to dissuade people from looking for additional interpretations of data.
That is how I view it. There is data, there are interpretations of it. No one view can be used to exclusively rule out all other views provided there is any space at all for the other view. Epicycles used to explain the motion of the planets. The Catholic Church did not have a problem with the solar-centric model until Galileo made an ass of himself at a party where a Cardinal was present. It is too early to be forcing the Faith on young Vuk. Physicists, above all, should be quite comfortable entertaining mutiple explanations of events simultaneously. In fact it is a pre-requisite if they want to use both Quantum Mechanics and General Relativity.
You shouldn’t spread this misleading stuff, either.
I am not surprised that you are not aware of the changes in Earth’s core AM, not being of your particular interest, but if you whish you can get data from one of the authors including Dr.A. Jackson.
What does surprises me that in all of your solar science long carrier, you have not done spectral analysis of the Aa geomagnetic index
http://www.vukcevic.talktalk.net/Aa-CAM.htm
and if you did, you didn’t ask yourself where the second strongest component, with period of about 34 years comes from.
This component obviously doesn’t come from the sun, so it can be assumed it comes from the Earth.
“Number of oscillations originate at the boundary between Earth’s core and its mantle have been identified, travel inward toward the inner core with decreasing strength. Four of these oscillations were robust, occurring at periods of 85, 50, 35 and 28 years.” http://www.jpl.nasa.gov/news/features.cfm?feature=2420
I am also surprised that many other scientists, if done so, have not also asked themselves, what are the consequences of this on the Earth’s hydrosphere, particularly tidal mixing, and the equatorial oceanic energy flux.
It is a sad state, when a an engineer, using his mental idling time, has to remind an army of PhDs where to look for sources of the natural climate oscillations.
No, that is not all, there is far more to it, as I’ve said number of times, sun and Earth act in concert as it is clearly shown here:
http://www.vukcevic.talktalk.net/CET-NAP-SSN.htm
I am not ‘pushing’, ‘peddling’ or ‘misleading’ with ‘nonsense’, ‘spurious correlations’ and ‘pseudo-science’, and I am not even ‘danger to society’ may be only a ‘man of superior ignorance’.
What I am doing is trying to draw attention of those who have ability means and resources, of those to whom millions around the world look up for accurate information, what is in their data, known or unknown, and should be acted upon in a proper investigative manner.
My thanks for tolerance and hospitality to Mr. Watts. and the WUWT .
Hi Crispin
Not to worry, I can take it, Dr. S. is doing a great job in moving my ‘investigations’ forward. Occasionally we exchange emails, he is always courteous and helpful, perhaps the ‘public persona’ doesn’t entirely reflect really ‘kind and cuddly’ doc.
Crispin in Waterloo says:
July 5, 2012 at 10:01 am
I have observed that you are completely conventional in your approach to all matters of the sun (standard model and all that) except when it comes to those narrow topics in which you are innovating. You demand that everyone accept the conventional views of how the sun works, except those things you are investigating where ‘something new’ is being explored that does not already form part of the standard solar model. I have a problem, not with you, but with that approach to the arguments of others. The standard solar model contains many assumptions and guestimates. Coronal heating is one of the mysteries and there are unconventional views as to what might be causing it.
It is an overstatement to say that there are many assumptions etc. The standard model is based on observations and physical understanding, not on guesses and assumptions. There are things that are not well understood, e.g. the dynamo and coronal heating, as you note, but that we can even ask these questions is because we have a standard model.
This article about doppler shift being used to trace the point at which heating has taken place is very interesting. There may have been a ‘standard guess’ but being popular is not ‘truth’. The result of the work above does not explain the heating, yet. The fact is, coronal heating exactly matches the profile of a plasma current.
The use of ‘plasma current’ is misleading and connotates the wrong image. The corona is a dilute plasma and changes in the magnetic field drive temporary electric currents [this has been known for decades]. The current is very unstable and often short circuits causing explosions. Precisely where and how is active research [as it has been for decades].
I find it irritating that you harass Vuk so much, day in, day out, about his wide ranging exploration of correlations many of which I find fascinating and which point to possible alternative relationships that do not match the standard model. So what? There are so many unkowns to be bothered trying to dissuade people from looking for additional interpretations of data.
I certainly encourage people to look at these things, but also to learn from others and to refrain from pushing interpretations that violate known physics [chances that they discover new physics is remote] when this is pointed out.
vukcevic says:
July 5, 2012 at 10:24 am
you have not done spectral analysis of the Aa geomagnetic index
Of course I have and of all the other interrelated things
and if you did, you didn’t ask yourself where the second strongest component, with period of about 34 years comes from.
This is well-known period [the Brueckner period e.g. http://www.freefictionbooks.org/books/c/44387-climatic-changes-by-huntington-and-visher?start=15 ] found in many solar and cosmic ray phenomena, see also
This component obviously doesn’t come from the sun, so it can be assumed it comes from the Earth.
An example of your unwarranted, hasty, etc wrong conclusions based on lack of knowledge [and unwillingness to learn].
Ahluwalia has been pushing his 3-cycle period for years e.g. http://adsabs.harvard.edu/abs/2010AIPC.1216..671A
Nothing new there.
What I am doing is trying to draw attention of those who have ability means and resources, of those to whom millions around the world look up for accurate information, what is in their data, known or unknown, and should be acted upon in a proper investigative manner.
I’m sure that they are fully aware of what is in their data. Looking through your stuff does not reveal anything worth investigating. Scientists usually choose to invetstigate something they see promise in and makes sense. You fall short on that.
Making a scientific discovery or finding a new effect happens perhaps once or twice in a scientist’s life and is very hard to pull off.
One thing is to think you have something, it is quite another to stay with long after it has been shown to be invalid.
@vuk
I am sure you can take it, as is evidenced by your good-natured responses. I don’t want to ‘punish’ people becaues of them communication in a second language either – that is easily done by not taking things in context. I spent most of my life working in other-language environments and one has to listen with a forgiving ear to the intent even if the language is a bit gruff. I am happy to hear you are on a good-natured corresponding basis. I maintain similar relationships in another field.
There is a great deal to read on the sun and solar workings – certainly I have done a lot of that for decades. All dominant paradigms fall to new ideas. It is unfortunate that science has to progress (so people say) by the death of the old guard when the oldest guard should be encouraging the young ones to look past any current understanding.
In this regard, the unexpected explosion of SN1987A deeply challenges the Solar Model because something that spectacular and ‘taht impossible’ should not happen but manifestly did. That single event alone, followed by the sound of breaking backs as solar physicists bent over backwards to try to fit it into the standard model, should be enough to keep the doors of future understanding wide open. It is best ‘dealt with’, apparently, by ignoring the implications. That is silly. The pinch effect is patently obvious in the resultant gas cloud. The ‘standard model explanation’ is just as patently unbelievable.
The mechanisms and implications of the cycles that are rooted in the magnetic field of the Earth are to say the least, poorly understood. I can’t see any gain in dismissing investigative flights of fancy. If Einstein had thought that way he would have ended his career still reviewing patents.
Crispin in Waterloo says:
July 5, 2012 at 11:56 am
If Einstein had thought that way he would have ended his career still reviewing patents.
It is a sure sign of a crank when comparisons are made with Einstein, Galileo, and other luminaries.
Crispin in Waterloo says:
July 5, 2012 at 11:56 am
All dominant paradigms fall to new ideas.
This is not true in modern science. New paradigms incorporate the results of the old. General relativity did not overthrow Newtonian mechanics, but extended the domain to include strong gravity, etc.
Crispin in Waterloo says:
July 5, 2012 at 11:56 am
In this regard, the unexpected explosion of SN1987A deeply challenges the Solar Model because something that spectacular and ‘taht impossible’ should not happen but manifestly did. That single event alone, followed by the sound of breaking backs as solar physicists bent over backwards to try to fit it into the standard model, should be enough to keep the doors of future understanding wide open.
And while I’m at it: SN1987A did not overthrow the standard model in any way. What happened was that astrophysicists discovered that the standard model was also applicable in situations they had not considered yet, so SN1987A was rather a triumph of the standard model.
@Leif
“And while I’m at it: SN1987A did not overthrow the standard model in any way. What happened was that astrophysicists discovered that the standard model was also applicable in situations they had not considered yet, so SN1987A was rather a triumph of the standard model.”
Right… Lee Smolin lives here in Waterloo and has a few choice things to say about standard models. No matter what is discovered in the world of subatomic particles, String Theory has a way to explain it with a new type of string or failing that, a new dimension. Everything is a triumph of String Theory. Even finding 10 types of Higg’s Bosons wil be a triumph of the Standard Model and String Theory.
RE Einstein and my use of him as an example, he was not extending Newton. He was overthrowing the idea that the universe was machanical. There is no way to reach Relativity by examining Newtonian ideas. That was my point and it was appropos.
Calling someone a crank is only helpful to a weak argument.
Leif Svalgaard says:
July 5, 2012 at 11:46 am
This is well-known period [the Brueckner period e.g.
Not so fast.
– Cosmic rays are more affected by changes in the Earth’s magnetic field than the solar wind.
You may say we know what the magnetic field was.
Slow down.
– we did not know that the Earth’s field oscillates with 34 year period until recently, and you still deny it, or may be not now I brought it to your attention. Do you agree or not ?
If indeed it is correct that the sun also oscillates with 34 year period, and now we know the Earth’s field does:
– the sun controls the Earth or
– the sun and the Earth are controlled by another unknown cause.
Whatever real cause is, there is strong climate cycle at about 34-5 years, it needs looking into.
You may disagree in the defense of your ‘status quo science’ but I don’t buy it.
From Leif Svalgaard on July 5, 2012 at 12:09 pm:
This quote must be remembered for 20-30 years from now when comparisons are made here to Leif Svalgaard.
Leif Svalgaard says: July 5, 2012 at 11:46 am
…………..
I’ve just red your Brueckner link.
Free Fiction books indeed
What I am putting forward to you and the WUWT readers is far more superior and sound science.
If you whish to overturn what I am putting forward, do make an effort to come up with something scientifically more superior and better documented by data, rather than ‘hear-say’ evidence.
I spent some time searching Google and Google Scolar for the Brueckner 30 + year cycle science references
Results are embarrassingly inadequate.
So I shall draw yours and others attention to data analysis from well known scientists :
Jeremy Bloxham
Andrew Jackson
David Gubbins
based on theoretical work of
Jault Gire and LeMouel
As presented here:
http://www.vukcevic.talktalk.net/Aa-CAM.htm
Crispin in Waterloo says:
July 5, 2012 at 1:03 pm
Right… Lee Smolin lives here in Waterloo and has a few choice things to say about standard models. No matter what is discovered in the world of subatomic particles, String Theory has a way to explain it
String Theory is not the standard model.
RE Einstein and my use of him as an example, he was not extending Newton. He was overthrowing the idea that the universe was machanical. There is no way to reach Relativity by examining Newtonian ideas. That was my point and it was appropos.
My point was that for the vast majority of calculations today that involve gravity and space and time [e.g. building a bridge or an elevator], Newton is used because he is good enough
Calling someone a crank is only helpful to a weak argument.
The person invoking Einstein et al. is the one exposing himself as the crank.
vukcevic says:
July 5, 2012 at 1:15 pm
Not so fast.
– Cosmic rays are more affected by changes in the Earth’s magnetic field than the solar wind.
Another example of shear ignorance of proportions. On the time scale of the Brueckner period the cosmic rays are not measurably influenced by the Earth’s magnetic field as the changes of the field are much too small.
– we did not know that the Earth’s field oscillates with 34 year period until recently, and you still deny it, or may be not now I brought it to your attention. Do you agree or not ?
The 34 years is but one of several and the Earth’s magnetic field does not oscillate as such, but some of the many tiny variations have that period among many others.
– the sun controls the Earth or
– the sun and the Earth are controlled by another unknown cause.
This is a typical exhibition of unscientific nonsense. Most likely they are just coincidences.
Whatever real cause is, there is strong climate cycle at about 34-5 years, it needs looking into.
This has been done a long time ago, and there is nothing there, which is why we no longer bother with it. Bruckner published a lengthy book in 1890 on the 35-yr cycle in weather and climate. H.W. Clough looked into this too. Today, none of this is believed to be valid, but is certainly well known.
You may disagree in the defense of your ‘status quo science’ but I don’t buy it.
There is no such thing as ‘status quo science’. Science is self-correcting and invalid claims are eventually filtered out. What you buy is not important, because you lack the ability to judge these things.
vukcevic says:
July 5, 2012 at 1:49 pm
What I am putting forward to you and the WUWT readers is far more superior and sound science.
I refer you to the above discussion about Brueckner. What you do is not science, not even reasonable conjecture.
If you whish to overturn what I am putting forward
I am trying to educate you. What you put forward invalidates itself when looked at in detail and with even a modicum of knowledge.
vukcevic says:
July 5, 2012 at 3:55 pm
data analysis from well known scientists :
Jeremy Bloxham
Andrew Jackson
David Gubbins
based on theoretical work of
Jault Gire and LeMouel
None of this even comes close to your ideas.
You should be ashamed of yourself trying to put these good folks in your box.
Verily, the Dunning-Kruger Effect is applicable in great measure in your case http://en.wikipedia.org/wiki/Dunning-Kruger_effect
I believe what people are trying to get through to you two is that we get tired of every article on anything to do with the sun turning into a war between the two of you. Yes there are different theories, get over each other. I check your site Lief, and yup I read Vukcevic’s too.. I think neither of you has the whole picture, but then who does. I am however tired of the nothing to see here, move along mantra.. there obviously is a whole lot more to see.
Hey, hey slow down.
I am just using data, showing the content and commenting on it.
Data from
Jeremy Bloxham
Andrew Jackson
David Gubbins
have reveled even more than they realized
http://www.vukcevic.talktalk.net/Aa-CAM.htm
so did data from Dr. Svalgaard, and
Wang, Lean, and Sheeley
as shown here:
http://www.vukcevic.talktalk.net/Aa-TSI.htm
I do not whish to comment on irrelevancies, just data and methods used to analyze it.
Science will be moved forward, no man is big enough to stop it.
Sun and Earth will do their thing; we are just transient minions, fortunate to be given power of reason to try understand it, but our reasoning right or wrong can’t change it.
See you, when you are of a happier disposition, got more work to do.
I quite like the battle my self as i’m not well up on accepted solar physics nor Vuk’s detours and have enjoyed a free education on the former since 2008 from Leif on a regular basis. But Vuk’s smacked down ideas keep going back to the corner and then coming limping back to life for another round. This is Vuk’s peer review process here and he hasn’t made it. Vuk needs to stop recycling as it’s tedious as it’s the same ol’ same ol’. One prior adherent to the Electric Universe idea received a life time ban for tedious repetition of the idea. There are forums for this such as tallbloke’s but Leif is a incredible resource for this site and keeps the Solar issues, which are fascinating to us vunerable lay people, on the straight and accepted narrow.
I quite like the battle my self as i’m not well up on accepted solar physics nor Vuk’s detours and I have enjoyed a free education on the former since 2008 from Leif on a regular basis. But Vuk’s smacked down ideas keep going back to the corner and then coming limping back to life for another round. This is Vuk’s peer review process here and he hasn’t made it. Vuk needs to stop recycling as it’s tedious as it’s the same ol’ same ol’. One prior adherent to the Electric Universe idea received a life time ban for tedious repetition of his pet theory. There are forums for this such as tallbloke’s but Leif is a incredible resource for this site here and keeps the Solar issues, which are fascinating, on the straight and accepted narrow. We should have a ‘electric universe’ thread with the idea that the electric universe idea be limited to that thread but be banned from solar threads.
I’m putting my head above the parapet fully expecting to get well and truly smacked down.
Didn’t someone before Einstein was even born come up with e=mc^2 using purely Newtonian physics? I think his name was Weiss or something similar.
I just seem to recall seeing it in a mid 1920s copy of the British Pharmacopoeia.
DaveE.
What doesn’t seem reasonable to me is that the sun’s core be hydrogen. Where did the heavier elements go? It seems unavoidable that there must be a core of heavier elements, similar to what we see in the planets with high core temperatures. I’m not trying to say the sun is made of iron. Only that there must be a core of heavier elements.
ferdberple says:
July 9, 2012 at 8:50 am
What doesn’t seem reasonable to me is that the sun’s core be hydrogen. Where did the heavier elements go?
The core is hydrogen mixed with helium. Some of the helium is primordial and was generated during the Big Bang and the rest is generated by nuclear fusion of hydrogen. There is a small admixture of heavier elements [of the order of 1%], but one could hardly call that a ‘core of heavier elements’.
According to NASA the sun is 71% hydrogen and 27% helium by mass in the visible region.
http://imagine.gsfc.nasa.gov/docs/ask_astro/answers/961112a.html
Given the large amount of helium present by mass, it seems almost certain that the core is mostly helium. In that case the hydrogen fusion must be primarily located outside the core. In which case the solar spectrum would be a fairly poor indication of the composition of the core.
ferdberple says:
July 9, 2012 at 6:12 pm
Given the large amount of helium present by mass, it seems almost certain that the core is mostly helium. In that case the hydrogen fusion must be primarily located outside the core.
No, as long as there is enough hydrogen for the fusion it will stay where it is. In the core, the abundance of helium by number is 10% that of hydrogen, so 90% if the nuclei are still hydrogen. The fusion process also needs the high temperature that there is in the core. In the convection zone the helium abundance by number is about 8%
In which case the solar spectrum would be a fairly poor indication of the composition of the core.
It is almost impossible to detect helium in the solar visible spectrum as the temperatures are too low for helium to be excited. The exception is during very strong solar flares, when one finds about 8% He by number in the photosphere. In the chromosphere, corona, and solar wind we can readily see the helium. It is there about 5% by number [with a solar cycle variation], reflecting the fact that it is harder to lift the heavier nuclei out against gravity.
In the core, the abundance of helium by number is 10% that of hydrogen
===
Water molecules make up something like 99% of the molecules in the human body by number, but only 70% by mass. Doesn’t counting the number of molecules understate the significance of mass in determining the characteristics of an object?
Given the large percentage of helium by mass, I would expect gravitational enrichment of the core to be higher than 10/8. How was this measured?
In the absence of significant convection at the core, the fusion waste products should collect at the core, inhibiting fusion in that area. Under that situation the most active fusion should be outside the core.
Thus, the notion that the convection zone is relatively shallow seems reasonable if the core is not the primary source of fusion. Rather that the most active fusion area is a sphere surrounding the core, with the convection zone above that.
ferdberple says:
July 10, 2012 at 6:56 am
Doesn’t counting the number of molecules understate the significance of mass in determining the characteristics of an object?
no, not when it comes to judging if fusion is still taking place. 90% of the particles in the core is hydrogen. If you assume that 1% is Uranium, that would cut the hydrogen content measured by mass in half, but hardly make a dent in the fusion rate which still is controlled by the remaining 89% hydrogen.
Given the large percentage of helium by mass, I would expect gravitational enrichment of the core to be higher than 10/8. How was this measured?
The observed luminosity has to match what is produced in the core. It does that best with the 10/8 ratio. Also, considering the amount of helium produced in the last 4.6 billion years leads to the same result.
In the absence of significant convection at the core, the fusion waste products should collect at the core, inhibiting fusion in that area. Under that situation the most active fusion should be outside the core.
They do collect in the core, but there is enough hydrogen left [90%] that fusion is not inhibited. Also, the speed of the thermal random motions is very high [620 km/s] so helps in mixing the material.
Thus, the notion that the convection zone is relatively shallow seems reasonable if the core is not the primary source of fusion. Rather that the most active fusion area is a sphere surrounding the core, with the convection zone above that.
much as you would like so, it just ain’t so. The fusion rate depends on the amount of hydrogen [still high, 90%] and the temperature [very steep dependence, something like temperature to the 4th power if memory serves] which is only high enough in the core.