From the National Science Foundation:
Answer lies in jets of plasma
One of the most enduring mysteries in solar physics is why the Sun’s outer atmosphere, or corona, is millions of degrees hotter than its surface.
Now scientists believe they have discovered a major source of hot gas that replenishes the corona: jets of plasma shooting up from just above the Sun’s surface.
The finding addresses a fundamental question in astrophysics: how energy is moved from the Sun’s interior to create its hot outer atmosphere.
“It’s always been quite a puzzle to figure out why the Sun’s atmosphere is hotter than its surface,” says Scott McIntosh, a solar physicist at the High Altitude Observatory of the National Center for Atmospheric Research (NCAR) in Boulder, Colo., who was involved in the study.
“By identifying that these jets insert heated plasma into the Sun’s outer atmosphere, we can gain a much greater understanding of that region and possibly improve our knowledge of the Sun’s subtle influence on the Earth’s upper atmosphere.”
The research, results of which are published this week in the journal Science, was conducted by scientists from Lockheed Martin’s Solar and Astrophysics Laboratory (LMSAL), NCAR, and the University of Oslo. It was supported by NASA and the National Science Foundation (NSF), NCAR’s sponsor.
“These observations are a significant step in understanding observed temperatures in the solar corona,” says Rich Behnke of NSF’s Division of Atmospheric and Geospace Sciences, which funded the research.
“They provide new insight about the energy output of the Sun and other stars. The results are also a great example of the power of collaboration among university, private industry and government scientists and organizations.”
The research team focused on jets of plasma known as spicules, which are fountains of plasma propelled upward from near the surface of the Sun into the outer atmosphere.
For decades scientists believed spicules could send heat into the corona. However, following observational research in the 1980s, it was found that spicule plasma did not reach coronal temperatures, and so the theory largely fell out of vogue.
“Heating of spicules to millions of degrees has never been directly observed, so their role in coronal heating had been dismissed as unlikely,” says Bart De Pontieu, the lead researcher and a solar physicist at LMSAL.
In 2007, De Pontieu, McIntosh, and their colleagues identified a new class of spicules that moved much faster and were shorter-lived than the traditional spicules.
These “Type II” spicules shoot upward at high speeds, often in excess of 100 kilometers per second, before disappearing.
The rapid disappearance of these jets suggested that the plasma they carried might get very hot, but direct observational evidence of this process was missing.
The researchers used new observations from the Atmospheric Imaging Assembly on NASA’s recently launched Solar Dynamics Observatory and NASA’s Focal Plane Package for the Solar Optical Telescope (SOT) on the Japanese Hinode satellite to test their hypothesis.
“The high spatial and temporal resolution of the newer instruments was crucial in revealing this previously hidden coronal mass supply,” says McIntosh.
“Our observations reveal, for the first time, the one-to-one connection between plasma that is heated to millions of degrees and the spicules that insert this plasma into the corona.”
The findings provide an observational challenge to the existing theories of coronal heating.
During the past few decades, scientists proposed a wide variety of theoretical models, but the lack of detailed observation significantly hampered progress.
“One of our biggest challenges is to understand what drives and heats the material in the spicules,” says De Pontieu.
A key step, according to De Pontieu, will be to better understand the interface region between the Sun’s visible surface, or photosphere, and its corona.
Another NASA mission, the Interface Region Imaging Spectrograph (IRIS), is scheduled for launch in 2012 to provide high-fidelity data on the complex processes and enormous contrasts of density, temperature and magnetic field between the photosphere and corona. Researchers hope this will reveal more about the spicule heating and launch mechanism.
The LMSAL is part of the Lockheed Martin Space Systems Company, which designs and develops, tests, manufactures and operates a full spectrum of advanced-technology systems for national security and military, civil government and commercial customers.
-NSF-
Discover more from Watts Up With That?
Subscribe to get the latest posts sent to your email.
steveta_uk,
” Perhaps this says more about you than about scientists?”
Perhaps it says more about what we in the US have been seeing in many science fields for years. People ideologically, monetarily, and SAFETY driven rather than driven by an interest in the best Science that can be practiced.
I would point out that we have been seeing some of the same through Climate Gate that isn’t primarily a US problem also. Then there is the IPCC which is truly a multi-national effort in corruption like virtually everything else done around the UN!!
Having read a bit on the subject it is clear to me the search for an explanation for the high temperatures in the corona must continue. Basically the claim is that jets hot enough to maintain the coronal temperature leap from a 6000 C surface and maintain a much larger surface at 2 million degrees. Ri-i-ight.
If one were to claim that the spicules are in fact conducting large currents, which would provide the energy in an electrical form rather than from thermal mass, the question arises as to what is driving that enormous current.
It seems more likely that the charge maintained by the corona relative to the surface draws the spicules aloft rather than they are driven upwards from below.
I remind readers that a plasma does not contain ‘particles’ in the regular sense. Think quantum fields and field effects. Waves, not bits. If it is hot and tenuous, it can still be electrically conductive.
It would be interesting to know if the spicules are actually an electrical connection downwards providing heat to the surface. Does the surface heat up following a spicule connection?
Oh, and one other solar observation. When are they going to do some splainin’ bout those COOL areas seen under sunspots?
I think it is pretty funny. Plasma people gave the reason many years ago. Nobody listened. Now so called mainstream people have said the same. Is the mainstream claiming credit here?
What may not be commonly appreciated is that these spicules (and perhaps “ordinary” ones at that) can increase the coronal temperature by energy addition. Any spicule will inject a mass of plasma into the corona with a velocity that will be dissipated by viscous effects. All the kinetic energy of the spicule will be transformed into thermal energy of the plasma. The question then becomes: what is the population of the plasma at that energy level? A Maxwellian temperature distribution will mandate a particular population density at a given energy. If the population is locally higher than that (by virtue of high-speed spicule deposition), the energy must equipartion through subsequent collisions. This can result in readjustment of the population energy spectrum…which means the temperature can increase. Such a process can continue until the energy loss mechanisms balance the energy addition, and the temperature reaches an equilibrium level.
Please don’t confuse this process with the ordinary thermal energy equilibriation process of dumping a pint of cold water into a bucket of warm water (as the conventional remarks about the “ordinary” spicules seem to reflect). If the kinetic energy of the cold water was high enough, the combined mass would be turned to steam. It is well known in weapons engineering that, above a certain projectile velocity, there is no point to incorporating any explosive in the projectile, because the specific kinetic energy of the projectile is greater than the specific heat of explosion of TNT. This is the mechanism of depleted uranium kinetic energy penetrators: once they hit the target, they convert to molten metal during the penetration and finally exit as hot uranium vapor and droplets.
Another example of this effect is the fact that helium “boils away” from our atmosphere into space. The fact that helium is at ambient air temperature means only that its atoms are distributed across the kinetic energy spectrum in a Maxwellian manner. The helium atoms above escape velocity go into space. Since their departure depletes the distribution, the distribution readjusts to move more helium atoms into that part of the spectrum, and the boil-off process continues. (Which is why we hoard helium in underground storage; it cannot be recovered from the atmosphere.)
Still another example of the general point is that one can use high-intensity infrared radiation to heat an object to a temperature at which that object would emit ultraviolet radiation (I’ve seen this done: the creation of artificial lightning bolts in open air). From the Stefan-Boltzmann law, this sounds like something at a “lower” temperature causing something to assume a “higher” temperature, but it would be a misreading of what is going on. The issue is energy addition and reaching an equilibrium with loss processes.
So essentially they just need some more cash to really figure out what’s what before they need even more cash to start figuring out why, and later more cash to why that is, and then some more to really truly understand it all, plus some extra to put it all together . . . At age 65 they give thanks and tell everyone to have a blast and don’t spend all the money at once.
@NSF
> In 2007, De Pontieu, McIntosh, and their colleagues identified a new class of
> spicules that moved much faster and were shorter-lived than the traditional
> spicules.
Hmm, I’m a bit skeptical about this. It’s true that ordinary spicules cover the entire sun (like blades of grass cover your lawn). But the ‘plasma jets’ depicted in the figures at the top of the article appear to be those associated with “active regions” like sunspots etc. So these would not blanket the entire chromosphere and would still leave the question begging for areas outside of the active regions.
This is a press release, so might be a case where the reporter got his facts mixed up after interviewing the scientists.
Dr. Svalgaard, what is your take on this article?
From the posted article:
“The high spatial and temporal resolution of the newer instruments was crucial in revealing this previously hidden coronal mass supply,” says McIntosh.
“Our observations reveal, for the first time, the one-to-one connection between plasma that is heated to millions of degrees and the spicules that insert this plasma into the corona.”
These seem to be the money quotes in terms of the actual proposed mechanics.
But what does it say?
Simply that these spicules provide the “mass” for the corona.
But that does not explain the temperature.
Now, the actual peer-reviewed paper in Science might have the missing observations & measurements and analysis & interpretation which explains how the spicules transfer energy into the corona from the photosphere or from below it (according the “nuclear furnace” model).
But this press release doesn’t supply that information.
Instead, readers are supplied with an unsupported conclusion, really just an assumption, which given the comments so far, it seems readers have implicitly picked up on.
Is the energy “concentrated” in the spicules, somehow, then released into the corona?
It isn’t explicitly stated.
Why the “we have the mystery solved” headline atop the press release?
Because this conundrum (6,000 degree photosphere, two million degree corona) threatens the mainstream model.
Perhaps, there is pressure from an alternative hypothesis that would upset (a lot of) somebodies applecart.
A poorly explained press release is worse than no press release at all.
Why?
Because then credibility is sacrificed and once lost is hard to get back.
Right, so we have observed a new phenomena and we can rush into fevered speculation about what it might do and this will keep us going to the next new phenomena which we can spin out to the next ……. (this is how our science progresses says -insert National Scientific Body here)
I thought the sun’s outer surface was hot because it’s made of CO2
John Day says:
January 7, 2011 at 2:18 pm
Dr. Svalgaard, what is your take on this article?
The plasma in the spicules has a range of temperatures, most of it below 100,000K, but enough of the plasma has temperatures above 1 million K that when injected into the corona it simply heats the corona [pouring hot water into cold]. One must remember that the corona is VERY tenuous and the chromosphere [with the spicules] is much denser and has much, much more mass that the corona, so it doesn’t take much. Actually most of material in the spicules falls right back onto the Sun, but enough [and it only takes a small fraction] makes it into the corona. Hot gas expands and if hot enough can escape the gravitational clutch of the Sun, resulting in the solar wind. The headline is a bit overhyped, but so are they all.
The problem has not really been solved, just moved to the spicules.
Okaaaaay…as I understand it, the surface of the sun is 6,000 degrees while the corona is a couple of millions of degrees. Assuming that the corona isn’t plugged into Al Gore’s mantle, the question is why the corona is so hot. Except Vulk says that temperature really isn’t the correct measurment but rather the energy of the emitted waves(?) So, is there some mechanism for the heat of the spiricles to be translated into motion for photon emission? Or is that even an intelligent/relevant question.
I think Leif often claims more confidence in standard models than can be justified, but what he said here is fair and then some:
My contention is that electrical behaviour and plasmas in space have often been given short shrift in favour of the gravitational force. Gravity is certainly of profound importance, and lends itself to nicer, neater equations, but cosmic plasmas seems to also be ubiquitious, and electrical force underrated at the large scale.
It’s certainly not my contention that the “Electric Universe” model is correct in all respects. I disagree vehemently with its most well known proponents on some tangential issues, and am still learning about the core issues.
However, I firmly believe they’re right insofar as electricity and plasmas in space are not fully understood, and of greater importance than most people realize, even if their theories ultimately don’t stand up.
I still think they’ll have made a contribution, and it behooves us to maintain an open mind, particularly when the standard models’ predictions don’t always work, the electric models’ (plural: there are different electric models) predictions sometimes do, and much is unknown and unsettled.
I am very suspicious of “settled science”. I prefer curious science.
“Anthony seeks to put the debate to rest with a strongly worded headline.”
No, Anthony used the headline from the press release, itself.
There is a controversy between two rival schools of thought (contrary to what some from the “magnetic reconnection” camp would have you believe):
From Interspace News (February 27, 2008):
“There is a lot of excitement over this project [THEMIS] in the research community, [Dr. Vassillis] Angelopoulos [THEMIS principal investigator at University of California Berkeley’s Space Sciences Laboratory in Berkeley, Calf.] said. For more than three decades, scientists around the globe have been embattled about where these lights originate so brilliantly and suddenly. And like the two polar caps at opposite ends of the planet, there are also opposing viewpoints.”
So, the THEMIS principal investigator for NASA knows there are opposing schools of thought.
Back to the news article:
“In the Reconnection Theory camp, members say the magnetosphere on the night side is like two rubber bands that stretch, snap and then reconnect into “U” shape bands that release their energy — much like a slingshot. That action would then accelerate the particles toward Earth causing the light show.”
“On the other side of the hypothesis is the Current Disruption Theory, which says at the onset of a substorm, higher frequency instabilities are excited so that the plasma and electromagnetic field form a turbulent state, which then short circuits the current that is now forced to go directly into the atmosphere. This current accelerates the electrons that in return cause the light show.”
http://www.interspacenews.com/FeatureArticle/tabid/130/Default.aspx?id=524
Two schools of thought: The Magnetic Reconnection Theory versus The Current Disruption Theory.
Oh no! The Sun’s atmosphere is hotter than it’s surface? Alarum! Solar Warming! We’re all going to die!
Sorry, it’s Friday night with a nice warming Scotch in a cold Canadian snowfall.
Actually, it is interesting to ponder this: The “We’re all goinjg to die” brigade often advocate the reduction of the human population to prevent us all from dieing
Thanks for a good science story. We so often get into polemics, it’s good to get back to some basic science, in a field where it is still OK to say “We don’t know”.
Grey Lensman: Problem NOT solved, only further conjecture. How can a hot plasma jet exit a cold surface overcoming massive gravity? poorly put I know but several posters here nail the oddities.
Youth, this kind of muddied thinking is inexcusable for a Lensman! If you are to triumph against Boskone you must learn not to jump to conclusions, but to truly think!. Consider the following:
Sol’s gravity isn’t that strong. Wikipedia reckons the escape velocity for Sol is only 617.5km/s. Sounds impressive, but just remember how much sheer mass gets hurled out during a coronal mass ejection or similar – which have velocities of between 20km/s and 3200km/s (!). And the average CME has a mass of 1.2 trillion kg.
As for these spicules, the real question is just where the energy comes from (please bear in mind I’m not a scientist, merely working this out as I go along & reading around for it). Some things to consider:
1. Magnetic currents powered from deep within the sun stirring up the surface plasma in a particular region – that is, transferring energy to the hot gases near the surface. Whilst some of this energy would be lost to the surrounding gases, we’ve seen with CMEs that magnetic fields can do this on a colossal scale, so assuming that it can happen on a smaller scale (and regular spicules are on the order of 500km in diameter and 10,000s of km long, so “small” is relative) seems reasonable.
2. Shockwaves in the hot gases near the surface. It’s a fairly well known phenomenon that if you compress a gas, you heat it up. Apply a shockwave in one direction and you’ll heat up the gas and – due to inertia – encourage it to find a new equilibrium by expanding in the direction of the shockwave.
3. Remember that the spicules don’t need to entirely overcome gravity. They can fall back into the photosphere later (or for that matter, disappear off into the sunset to join the solar wind), just so long as they first dump a lot of energy into the corona.
As also noted above, the corona really is very (VERY) thin. Wikipedia reckons it to be one trillionth the density of the photosphere… itself a fraction of the density of Earth’s sea level atmosphere (2e-4kg/m^3 vs 1.2kg/m^3).
In other words, there’s not very much of a corona – size (or at least volume) is in this case very deceptive. Adding 1 litre of boiling water to a swimming pool with only 100 litres of cold water in it will have a much greater effect on temperature than doing the same to the same swimming pool when it’s full.
“The findings provide an observational challenge to the existing theories of coronal heating.”
Observation of the real world – what a novel concept for theoreticians.
Electric forces are 10^39 stronger than the gravitational force, so overcoming “massive gravity” is not a problem for solar plasma eruptions.
“No, Anthony used the headline from the press release, itself.”
Well, okay, fair observation, and I stand corrected. Nonetheless, the headline is wrong-headed, and it shouldn’t surprise me that it comes from a government agency.
This is a promising theory, but it’s way premature to say that.
Mark
Thank you, I specialise in thinking outside the box but do not wish to do others thinking for them. Thus I asked them to think.
Thinkers know that the universe functions on simplicity, simple is simple does. Thus the simplest explanation of what you see is Most probe the correct solution.
Thus in the case of the sun, what you see can be replicated and scaled in the lab, simply, using electricity and magnetism.
QED
This is why I like this blog.
Many of the questions raised by readers here can be answered by reading this book:
http://www.amazon.com/Sun-Space-Astronomy-Astrophysics-Library/dp/3540669442
Are we divided by a common language in this argument?
I’ve been exploring the concept of ether in another discussion, and thought this is what was happening. Today I found this:
Ether space time and cosmology: new insights into a key physical medium
The necessity of ether is not questioned today even by those who pretend to do so but do not hesitate to attribute qualities to the vacuum. Ether theory plays a creative role, even if given different names: (vacuum, fundamental plenum or cosmic substratum).
Htt://www.ufindbook.com/ebook-science-engineering/ether-space-time-cosmology-new-insights-into-a-key-physical-medium.html
To take this further:
Relativity – Mass Increase is a FRAUD
Relativists, or more specifically, mathematicians, have no clue what the word MASS means. They have never defined this word consistently. This is why they use the word MASS synonymously with WEIGHT, and with a multitude of many other terms as well, …. and they do so whenever it suits their arguments!
http://hubpages.com/hub/Relativity-Mass-Increase-is-a-FRAUD
Apart from the shouting, what think ye all of this? Is this true?
James F. Evans says:
January 7, 2011 at 4:26 pm
There is a controversy between two rival schools of thought (contrary to what some from the “magnetic reconnection” camp would have you believe)
There are not two schools of thought. These things are the result of electric currents [and their rapid changes]. The currents are driven by transient electric fields [there are no other kinds] which are created by a variety of processes involving plasma moving in and across magnetic fields [induction, reconnection, etc]. We have discussed this so many times. Go back and review some of all that nauseating detail.
Robert of Ottawa says:
January 7, 2011 at 4:59 pm
As also noted above, the corona really is very (VERY) thin.
As a good illustration, if you were standing on one of those spicules the pressure of the whole of the corona above you on your outstretched hand is smaller than the pressure under one foot of a tiny spider crawling over said hand on Earth.
Jack Simmons says:
January 7, 2011 at 8:10 pm
Many of the questions raised by readers here can be answered by reading this book
I can recommend that book strongly.