The Case of the Missing Sunspots: Solved?
Written by Anne Minard
The Sun has seen precious few sunspots (as shown in this NASA closeup) in the past year, and solar physicists have been working to understand why. Now, some think they have an answer.
According to work being presented this week at the meeting of the Solar Physics Division of the American Astronomical Society, a solar jet stream deep inside the Sun is migrating slower than usual through the star’s interior and it's at least associated with — if not causing — the current lull in sunspots and solar activity.
The Sun normally undergoes an eleven-year cycle of magnetic activity related to sunspots, solar flares, and the interplanetary storms called “CMEs." The current “solar minimum” quiet period has been unusually long and deep, confounding scientists who hope to understand the origins of space weather and the Sun’s magnetic field.
Rachel Howe and Frank Hill, both scientists with the National Solar Observatory (NSO) in Tucson, Arizona, used long-term observations from the NSO’s Global Oscillation Network Group facility to detect and track an east-to-west jet stream, known as the “torsional oscillation," at depths of ~1,000 to 7,000 km (about 600 to 4,000 miles) below the surface of the Sun. The Sun generates new jet streams near its poles every 11 years; the streams migrate slowly, over a period of 17 years, to the equator and are associated with the production of sunspots once they reach a critical latitude of 22 degrees.
Howe and Hill found that the stream associated with the new solar cycle has moved sluggishly, taking three years to cover a 10-degree range in latitude compared to two years for the last solar cycle, but has now reached the critical latitude. The current solar minimum has become so long and deep, some scientists have speculated the Sun might enter a long period with no sunspot activity at all. The new result both shows that the Sun’s internal magnetic dynamo continues to operate, and heralds the beginning of a new cycle of solar activity.
“It is exciting to see," said Hill, “that just as this sluggish stream reaches the usual active latitude of 22 degrees, a year late, we finally begin to see new groups of sunspots emerging at the new active latitude.” Since the current minimum is now one year longer than usual, Howe and Hill conclude that the extended solar minimum phase may have resulted from the slower migration of the flow.
GONG and its sister instrument SOHO/MDI measure sound waves on the surface of the Sun. Scientists can then use the sound waves to probe structures deep in the interior of the star, in a process analogous to a sonogram in a medical office.
“Using the global sound wave inversions, we have been able to reveal the intimate connection between subtle changes in the Sun’s interior and the sunspot cycle on its surface,” said Hill.
“This is an important piece of the solar activity puzzle,” added Dean Pesnell, of NASA’s Goddard Space Flight Center. “It shows how flows inside the Sun are related to the creation of solar activity and how the timing of the solar cycle might be produced. None of the forecasting research groups predicted the current long extended delay in the new cycle. There is a lot more to learn in order to understand how the Sun creates magnetic fields.”
The new science of helioseismology, enabled by instruments such as the ground-based GONG, the Michelson Doppler Imager aboard the SOHO spacecraft, and NASA’s planned Solar Dynamics Observatory, has revolutionized understanding of the solar interior. “While the surface effects of the Sun’s torsional oscillations have been observed for some time, understanding of the dynamo and the origin of sunspots depend on measurements of the solar interior that are only possible
with helioseismic techniques," said Hill.
Source: AAS Solar Physics Division Meeting (press release). Anne Minard is attending the meeting, and will report additional details from the teleconference on her blog at anneminard.com. Check back there after 2 p.m. Mountain. Also: check out this great movie!
Filed under: Astronomy, Solar Astronomy
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June 17th, 2009 at 12:02 pm
What is the closest we can get to the sun given today's technology and still send back pictures or any sort of scientific measurement? What is the highest resolution images we can theoretically take of the sun? Any ideas?
June 17th, 2009 at 2:44 pm
@ ND,
Check this out: NASA Plans to Visit the Sun.
June 17th, 2009 at 2:49 pm
And this: Solar Probe Plus (official site).
June 17th, 2009 at 2:52 pm
And also this: The Solar Probe (unofficial site).
June 17th, 2009 at 2:58 pm
neat! it says that the original Solar Probe mission proposed in 2005 intended to go to 4 Rs. The Plus mission will do ~ 8Rs at closest. But I can't wait until 2015!
I wonder if a suicidal mission that just plunges into the sun could be put together and launched faster.
June 17th, 2009 at 3:29 pm
ND:
I think that NASA prefers to leave Kamikaze missions to the Japanese.
June 17th, 2009 at 9:24 pm
seriously tho, some sort of mission like the probe dropped by Galileo could be interesting. Although I don't know how fruitful it could be and how close we can get before the instruments fry.
June 18th, 2009 at 10:07 am
ND
Probably you should build the probe with a material that withstands 7000K – this would be awesome, since the probe would actually dip into the sun.
However, the detection of the current leading to the spots is incredible. Hopefully we can find a connection between the currents and CME's – could be that such a connection would save us all, because we coud be able to predict a severe storm with time before it actually happens.
On the other hand, this finding of a "cause" of sun spots also causes a lot question – or, better said, pushes the questions to another topic. I posted them already in the corresponding article on BadAstronomy, but here they are again:
* What are these currents?
* What causes them to move?
* What causes them to reappeare every 11/22 years?
* What can cause a delay?
* Does the strength of the currents influence the number/power/size of the spots? Does it influence the strength of CMEs?
I guess one can think of a lot more questions. Many secrets to reveal – science will never run out of work
That’s good news!
June 18th, 2009 at 10:42 am
@ Ivan3Man:
Thank you for the links.
This in situ statellite probe should make observations & measurements that advance Man's understanding of the Sun's dynamics.
ND asked me on another post's thread what predictions I would make as to what the probe will find.
Good question.
Considering the payload from Ivan3Man's link:
"The payload consists mainly of instruments designed to sense the environment right around the spacecraft—e.g., a magnetometer, a plasma wave sensor, a dust detector, electron and ion analyzers and so on. "In-situ measurements will tell us what we need to know to unravel the physics of coronal heating and solar wind acceleration," she says."
The first prediction, maybe more a question, is will the probe find 'double layer' structure? This could account for the acceleration of charged particles away from the Sun (double layers are known to accelerate charged particles).
The double should be up in the corona located where the acceleration has been detected. To detect this double layer (if it exists) the probe must pass through the double layer to detect the electric field (from the links kindly provided by Ivan3Man, it's not clear whether it gets close enough).
Will the probe penetrate (Ivan3Man's favorite word) the region or layer where the acceleration occurs?
Perhaps, even the electric potential or voltage drop in the double layer can be observed & measured (again, if it exists).
I'm not clear on whether the in situ satellite probe will get close enough to detect double layers:
"The technique, called coronal tomography, is a fundamentally new approach to solar imaging and is only possible because the photography is performed from a moving platform close to the sun, flying through coronal clouds and streamers and imaging them as it flies by and through them."
This quote from NASA suggests the probe will go through prominences of the corona, but not necessarily into the corona itself (too hot at one million degrees, plus).
This probe should be able to provide additional data that reflects the Sun's electrical nature.
Obviously, another series of questions would be how the presummed driving force, i.e., an internal nuclear dynamo, accounts for these processes, or is there an alternative possibility of an external driving force (a frowned upon proposition) that offers a better explanation?
ND, you wanted predictions, and the above falls somewhat short of that.
But perhaps, the better stance is to be able to consider the data when it comes in with an open-mind with no preconceived ideas that straightjacket the analysis & interpretation. I know Ivan3Man and others would like to see me straightjacketed in a white padded room
June 18th, 2009 at 11:42 am
I should know the answer to this but the 1mil degree temperature of the corona really is not an issue given the low density of the corona. It's the 7K degree surface given the higher density of the surface that'll pretty much melt any material we send into it. Corrections are welcome.
As for the predictions, I guess my point is that those in the EU/PC camp with scientific background have the opportunity to put forth some substantive, quantifiable predictions since they are the ones pushing for the electrical nature of the sun. What do they expect to see given the path the probe will take, given their electrical model of the sun? Unfortunately I don't have the scientific qualities to judge such predictions but such predictions would be directed to the scientific community.
"open-mind with no preconceived ideas that straightjacket the analysis & interpretation."
One can present models and predictions and hold them up to observational results without any problems. But at the same time, this is uncharted territory given that no probe has come this close to the sun.
June 18th, 2009 at 12:02 pm
I have an even more basic question for Anaconda, ND, and it is this: what quantitative characteristics of the Sun's purported double layer are derivable from the so-called theories he's so keen on?
Recall that, AFAIK, there are no such theories at all, merely some wholly unappetising word salads, which leads to a situation that seems rather common …. namely that, after the fact, proponents can spin any results whatsoever to 'prove' their pseudo-science 'got it right', no matter what those results actually are!
In this case, we can ask a simple, yet powerful, question: how, in the view of the most accomplished EU/PC researcher(s)/scientist(s), could any probe of the kind being talked about in this thread detect (and measure) a 'double layer'?
And of course I don't mean word salad/handwaving how, I mean a concrete, specific, step by step account of the instrument(s) characteristics and the data analysis …
June 18th, 2009 at 3:13 pm
@ ND:
Yes, predictions can be made, while still retaining an open-mind and reasonable scepticism.
Science already knows there are electromagnetic structures around the Sun like sigmoids and a plasma torus (when the Sun is more active). Again, magnetic fields are derived from electric currents (electrons in motion). Not to mention Coronal Mass Ejections (CME) take the form of Birkeland currents upon transmission from the Sun to the Earth, they don't just travel as an amorphous cloud of plasma, but rather have a specific structure with defined dynamics.
In regards to Nereid's request of quantitative analysis, you have to make observations & measurements BEFORE you make quantitiative analysis.
Double layers will have different voltage drops between the electron and ion layers depending on the current density.
That is how NASA confirmed the electromagntism in the solar system from making in situ observations & measurements and then doing quantitative analysis.
Nereid, did NASA confirm electomagnetic processes and phenomenon in the solar system by "word salad/handwaving"?
No, NASA made in situ observations & measurements and then did quantitative analysis.
Nereid wrote: "namely that, after the fact, proponents can spin any results whatsoever to 'prove' their pseudo-science 'got it right', no matter what those results actually are!"
Isn't that the way NASA confirmed the electromagnetic processes in the solar system: Namely, they conducted the observations & measurements first?
Nereid wrote: "In this case, we can ask a simple, yet powerful, question: how, in the view of the most accomplished EU/PC researcher(s)/scientist(s), could any probe of the kind being talked about in this thread detect (and measure) a 'double layer'?"
You measure the voltage drop by passing a probe through the area where you suspect a double layer exists.
NASA has already done this with the Earth's magnetosphere and confirmed the presence of a double layer.
As an example, per the Wikipedia entry for plasma double layers: "The most definite proof of these structures was obtained by the Viking satellite, which measures the differential potential structures in the magnetosphere with probes mounted on 40m long booms. These probes can measure the local particle density and the potential difference between two points 80m apart. Asymmetric potential structures with respect to 0 V were measured, which means that the structure has a net potential and can be regarded as a double layer."
And the supporting peer-reviewed paper abstract:
http://adsabs.harvard.edu/cgi-bin/nph-bib_query?bibcode=1992ITPS…20..756B&db_key=PHY&data_type=HTML&format=&high=42ca922c9c00530
A quote from the abstract:
"The wave instrument on the Swedish Viking satellite performed measurements of plasma density and potential fluctuations with high temporal and spatial resolution. In the auroral regions, double-layer structures were observed which have scale lengths of about 100 m and where the plasma density is reduced by up to 50 percent."
June 18th, 2009 at 8:55 pm
"Double layers have different voltage drops
between the electron and ion layers depending on the current density" ?
I do know what you try to say, but what you wrote is not correct! That is not how electron flow works. Potential differences are only
present if there is an current flow! Density in plasma flow create these currents! Because
there seams to be opposing plasma flows
which create electricity! This is the principal
of how electricity works.
June 18th, 2009 at 10:39 pm
Bravehart:
I accept your critique and appreciate the correction.
June 19th, 2009 at 5:04 am
Well, Anaconda, this is a rather unlikely approach to testing your pet theory, isn't it?
After all, those who design the spacecraft and instruments must work within severe constraints, so they will focus on testing well-stated hypotheses.
Suppose there is a double layer (DL) … but the space probe's instruments cannot detect it; perhaps the DL is so 'strong' that it destroys the spacecraft (the mere fact of destruction would tell you nothing about any DLs, unless you had predicted that they'd likely be that 'strong' to start with); perhaps the DL is so 'weak' that it fails to register on the instruments (ditto); perhaps there is not one DL but thousands or millions (would the signal of such a thing be unambiguous, unless the instrument were designed with the possibility of encountering that?).
Further, without good planning and design, how could something which registers on the instruments as a possible DL but isn't be assessed?
June 19th, 2009 at 8:34 am
Anaconda: "But perhaps, the better stance is to be able to consider the data when it comes in with an open-mind with no preconceived ideas that straightjacket the analysis & interpretation."
You have not demonstrated this in all the months I've seen you post on the net. And I do not expect it in all your future UT posts.
June 19th, 2009 at 11:13 am
@ Nereid:
I agree, you are right on all your points, and I don't know if the satellite probe has been designed with detection of double layers as a possibility.
The fact that the Sun is electrical in nature is not so much in question as some of the noted phenomenon, such as the 6,000 K photospere (surface) temperature and the 2 million K corona , which is unexplained, as well as the acceleration of the solar wind, even though acceleration isn't partcularly noted at the surface.
My mentioning double layers was based on the known facts that double layers have been detected at the Earth's magnetopause and that part of a Birekeland current's structure is a Langmuir sheath (DL) that surrounds field-alinged current.
Could it be that the acceleration is also the reason for the increased temperature in the corona?
So possibly detection of double layers could explain two phenomenon at once, two birds with one stone.
I should add that the coronal loops are thought to be electrical in nature: "A long standing mystery in solar physics is why solar coronal loops typically have an axially uniform cross section;1 i.e., a filamentary shape…This paper argues that axial uniformity is the result of a rather complex sequence of events which occur whenever an electric current I is made to flow along an initially axially nonuniform, current-free, axisymmetric magnetic flux tube ~a process corresponding to injection of magnetic helicity into the flux tube!."
See, P. M. Bellan, "Why current-carrying magnetic flux tubes gobble up plasma and become thin as a result", Plasma Physics (2003):
http://authors.library.caltech.edu/1892/1/BELpop03.pdf
June 21st, 2009 at 1:07 am
I wonder if you could clarify what you mean here Anaconda?
AFAIK, the first isn't so much unexplained as there are too many possible explanations and not enough in the way of observations to rule most such explanations out, and the second? I didn't know it was unexplained at all!
(bold added)
I can't see how DLs could explain both, at least not without a model that is potentially quantifiable; has anyone published such a model?
June 22nd, 2009 at 12:11 pm
Anaconda:
Unexplained? "[T]he Sun is electrical in nature…"? My hairy ass! I went to great lengths to explain to you, Anaconda, the so-called "coronal heating problem" on the "Galaxies Grow From Black Hole Seeds" thread at Bad Astronomy, but you completely ignored it and now you're regurgitating the same 'electric' Sun bollocks here!
June 22nd, 2009 at 3:05 pm
@ Ivan3Man:
Not even Nereid disputes the Sun's electrical nature.
The open question is what causes all the electrical phenomenon.
See the below schematic of the Sun:
http://www.holoscience.com/news/img/Solar%20transformer.jpg
Did you even bother reading the link I provided that explained the electric current in the Sun's flux tubes. Apparently not.
Time for you to go back to class.
On another note:
Constant force X mass equals acceleration.
The solar wind (diffuse electric current) accelerates, so likely a constant force is being applied to it.
June 22nd, 2009 at 9:16 pm
Anaconda:
Yeah, I read it, but what the bloody hell has that got to do with an 'electric powered' Sun? I have electric currents flowing through the ring-mains of my house, but it does NOT flow on its own accord; it requires a power supply, so what the bloody hell is the alleged power source for the 'electric' Sun?
Furthermore, is the link to that half-assed schematic of the 'electric' Sun supposed to impress me? ROFLMAO!
So, Anaconda, how is it that the polar orbiting Ulysses spacecraft did not detect any inflowing electric current into the Sun's polar regions as allegedly portrayed in that schematic, then?
Also, you're a bloody hypocrite to complain when someone else doesn't read your links, and yet you don't bother to read the links that my associates and I provide for you. It is YOU who should go back to class!
June 22nd, 2009 at 9:58 pm
@ Anaconda,
RE: Your 'schematic' of the Sun link…
To paraphrase Crocodile Dundee: That's no Sun schematic; THIS is a Sun schematic! (Click on the image to embiggen!)
June 23rd, 2009 at 2:35 am
Anaconda, you have shown – repeatedly – that you do not understand (classical) electromagnetism.
When you use the term 'electromagnetism', you do so in a highly idiosyncratic way.
No surprise, then, to learn that what you understand when you read words like 'electrical' and 'magnetic' is likely to differ, possibly radically so, from what the authors who wrote those words intended, and what most readers understand when they read them.
If you think that the link contains a representation that I would, or might, agree with, well, you think wrong.
I do not know what that diagram has to so with the Sun, and have no idea where the person(s) who created it got the idea that the Sun is part of a giant electrical circuit from, but I do think it's fair to say that such a concept is inconsistent with huge numbers of very good observations*
You're in that alternate universe again Anaconda; this sentence is unintelligible …
The solar wind is NOT a "diffuse electric current", and it does NOT "accelerate" (at least, not in the manner you seem to imply).
Why do you seem to positively wallow in your ignorance?
*caveat: the diagram has no scale, nor are any items in it quantified … so, strictly speaking, as a stand-alone diagram it is scientifically meaningless (like the infamous 'Electric Comet').
June 23rd, 2009 at 3:23 am
@ Nereid,
Anaconda could not tell an electric current from a blackcurrant!
June 23rd, 2009 at 7:14 am
Anaconda,
When you say the solar wind accelerates, I'm guessing you mean as it travels through the solar system. If so, is there evidence for this?
June 24th, 2009 at 4:31 am
Anaconda: **CRICKETS**