Our resident solar expert, Dr. Leif Svalgaard, sends word of this new discovery.
Stanford solar scientists solve one of the sun’s mysteries
The sun’s magnetic field can play havoc with communications technology. Stanford scientists have now described one of the underlying processes that help form the magnetic field, which could help scientists predict its behavior.
By Bjorn Carey
Stanford solar scientists have solved one of the few remaining fundamental mysteries of how the sun works.
The mechanism, known as meridional flow, works something like a conveyor belt. Magnetic plasma migrates north to south on the sun’s surface, from the equator to the poles, and then cycles into the sun’s interior on its way back to the equator.
The rate and depth beneath the surface of the sun at which this process occurs is critical for predicting the sun’s magnetic and flare activity, but has remained largely unknown until now.
The solar scientists used the Stanford-operated Helioseismic and Magnetic Imager (HMI) – an instrument onboard NASA’s Solar Dynamic Observatory satellite – to track solar waves in much the way seismologists would study seismic movements beneath the surface of the Earth. Every 45 seconds for the past two years, the HMI’s Doppler radar snapped images of plasma waves moving across the sun’s surface.
By identifying patterns of sets of waves, the scientists could recognize how the solar materials move from the sun’s equator toward the poles, and how they return to the equator through the sun’s interior.
“Once we understood how long it takes the wave to pass across the exterior, we determined how fast it moves inside, and thus how deep it goes,” said Junwei Zhao, a senior research scientist at the Hansen Experimental Physics Laboratory at Stanford, and lead author on the paper.
Although solar physicists have long hypothesized such a mechanism, at least in general terms, the new observations redefine solar currents in a few ways. First, the returning currents occur 100,000 kilometers below the surface of the sun, roughly half as deep as suspected. As such, solar materials pass through the interior and return to the equator more quickly than hypothesized.
More startling, Zhao said, is that the equator-ward flow is actually sandwiched between two “layers” of pole-ward currents, a more complicated mechanism than previously thought, and one that could help refine predictions of the sun’s activity.
“Considered together, this means that our previously held beliefs about the solar cycle are not totally accurate, and that we may need to make accommodations,” Zhao said.
For example, some computer models projected that the current solar cycle would be strong, but observations have since showed it is actually much weaker than the previous cycle. This inconsistency could be due to the previously unknown inaccuracies of the meridional circulation mechanism used in the simulations.
Improving the accuracy of simulations, Zhao said, will produce a better picture of fluctuations of the sun’s magnetic field, which can interfere with satellites and communications technology on Earth. The sun’s magnetic field resets every 11 years – the next reset will occur sometime in the next few months – and there is evidence that changes in the meridional flow can influence how the magnetic field evolves during a particular cycle.
“We want to continue monitoring variations of the meridional flow,” he said, “so that we can better predict the next solar cycle, when it will come and how active it will be.”
The report was published in the online edition of The Astrophysical Journal Letters. It was co-authored by three other researchers at the Hansen Experimental Physics Laboratory – senior scientists Rick Bogart and Alexander Kosovichev and research associate Thomas Hartlep – as well as NASA senior scientist Tom Duvall. Phil Scherrer, a professor of physics at Stanford, is the principal investigator of the HMI project and supervised the study.
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Leif adds an excerpt from the paper in an email:
Meridional flow inside the Sun plays an important role in redistributing rotational angular momentum and transporting magnetic flux, and is crucial to our understanding of the strength and duration of sunspot cycles according to flux-transport dynamo theories. At the Sun’s surface and in its shallow interior to at least 30 Mm in depth, the meridional flow is predominantly poleward with a peak speed of approximately 20 m/s.
The poleward plasma flow transports the surface magnetic flux from low latitudes to the polar region, causing the periodic reversals of the global magnetic field, a process important to the prediction of the solar cycles. The speed and variability of the meridional flow also play an important role in determining the strength and duration of the solar cycles, and the unusually long activity minimum at the end of Solar Cycle 23 during 2007–2010 was thought to be associated with an increase of the meridional flow speed during the declining phase of the previous cycle. Therefore, an accurate determination of the meridional flow profile is crucial to our understanding and prediction of solar magnetic activities.
Although the poleward meridional flow at the solar surface and in shallow depths has been well studied, the depth and speed profile of the equatorward return flow, which is expected to exist inside the solar convection zone to meet the mass conservation, largely remains a puzzle. It is generally assumed that the return flow is located near the base of the convection zone, although no convincing evidence had been reported.
The continuous Doppler observations by the Helioseismic and Magnetic Imager onboard the recently launched Solar Dynamics Observatory mission (SDO) allow us to measure and detect the long-sought equatorward flow. Our analysis, which takes into account the systematic center-to-limb effect that was recently found in the local helioseismology analysis techniques, gives a two-dimensional cross-section picture of the meridional flow inside the nearly entire solar convection zone, and reveals a double-cell circulation with the equatorward flow located near the middle of the convection zone.
Figure 1 shows the new picture suggested by the HMI data.
This new picture of the solar interior meridional circulation differs substantially from the previously widely believed picture of a single-cell circulation with the equatorward flow near the bottom of the convection zone [the Conveyor Belt Model]. Through removing a systematic center-to-limb effect that was only recently identified, our analysis corrects and improves the previous solar interior meridional flow profile given by Giles (1999) using a similar analysis procedure.
The new meridional circulation profile poses a challenge to the flux-transport dynamo models, but provides more physical constraints to these models creating a new opportunity to further understand how magnetic field is generated and how magnetic flux is transported inside the Sun. Past dynamo simulations have already demonstrated that a meridional circulation profile with multiple cells might not be able to reproduce the butterfly diagram and the phase relationship between the toroidal and poloidal fields as observed, unless the dynamo model was reconsidered. However, on the other hand, solar convection simulations have shown the possibility of multi-cell circulation with a shallow equatorward flow (e.g.,Miesch et al. 2006; Guerrero et al. 2013), demonstrating that our analysis results are reasonable.
Moreover, a recent dynamo simulation, with the double-cell meridional circulation profile incorporated, showed that the solar magnetic properties could be robustly reproduced after taking into consideration of turbulent pumping, turbulent diffusivity, and other factors (Pipin & Kosovichev 2013). All these studies, together with our observational results, suggest a rethinking of how the solar magnetic flux is generated and transported inside the Sun.
Abstract: http://iopscience.iop.org/2041-8205/774/2/L29
pdf here: http://www.leif.org/EOS/ApJL-2013-Meridional-Flow.pdf
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Carla says:
August 30, 2013 at 6:39 pm
What if during the Maunder Min., the amount of cosmic rays in the solar neighborhood, were less than they are now, for this Modern Min.? Like maybe there are more now than then in the local solar neighborhood.
There were an excess of cosmic rays during the Maunder Minimum. There are indications that the excess may be climate related [solar activity is only one of several factors that determine the flux of cosmic rays that reach the atmosphere].
They have seen them coming from two different regions, GCR, plus the ACR (anomalous cosmic rays) factor.
The ACR have generally much lower energy than the CGRs and are not likely to have any climate effect or to affect the amount of 10Be and 14C generated.
Leif Svalgaard says:
August 30, 2013 at 6:44 pm
The ACR have generally much lower energy than the CGRs and are not likely to have any climate effect or to affect the amount of 10Be and 14C generated.
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Yes..those little understood ACR, some of which are produced by solar wind interactions in Earth’s magnetosphere.. and some of them accelerated from solar interactions with interstellar neutrals..yes the little understood, underestimated ACR..
I’m all good with the new model Dr. S., don’t see a problem with that..
.
Short wave IR energy drills deep into the equatorial ocean and can be stored in the ocean. However clouds mitigate the amount of SWIR that drills into equatorial ocean surfaces. These pools of warm or less warm water are globby pools that move along the currents that flow on top, in the middle, and along the bottom of the oceans. When these pools are at the surface, they become powerful sources of weather pattern variation changes that eventually even change the weather patterns over the equatorial oceanic belt, thus changing the cloud cover there. These moving, not well mixed, dynamic pools and waves are not cyclical nor do the effects they cause cancel each other out over time. Which is why you can have randomly occurring short term weather pattern variation change or long term weather pattern variation change that can build on one another creating trends up or down.
That is where the drivers are in my opinion because this highly variable and powerful planet has the most plausible drivers of weather pattern variation change.
Leif Svalgaard says:
August 29, 2013 at 10:11 am
…
it takes 250,000 years for the energy released in the core to reach the surface, so we cannot say that the core processes explains 180/360 ‘cycles’.
Bill Illis
How long does it take for energy received from the Sun to migrate its way through all those land, water and atmospheric molecules back out to space.
For some it is immediately, for others [e,g, if it reaches the deep ocean of great depth on land] it can take thousands of years.
I thought of the same question but Bill beat me to it. If we restrict the question to IR photons (of the type absorbed by water vapour and CO2) emitted upwards at the earth surface (only air above them), what is the mean time of their escape from the earth’s atmosphere and the tortuosity of their path (actual path / straight line path)? Mean number of interactions?
Another question arising from this thought-provoking research – how do photons interact in a plazma? (Do you get photons in a plazma?) Clearly it is not atomic interactions of absorption / reemission/scatter.
By that you mean that the Maunder Minimum was a manifestation of a cyclic phenomenon?
“”””””……richardscourtney says:
August 30, 2013 at 1:14 pm
george e. smith:
At August 30, 2013 at 12:58 pm you ask kadaka (KD Knoebel) how he got a BA in physics.
Obviously, he qualified from one of the better English universities. They award BA – not BSc – degrees for science courses.
kadaka (KD Knoebel) was claiming he had obtained a ‘better’ science degree than a mere BSc from some ‘red-brick’ uni. but you failed to ‘get it’.
Richard……””””””
Well I only got an ordinary peasant BSc from an ordinary New Zealand University. They give bachelor of Science degrees to people who study science; not Arts,
And since all I studied for four years, was Physics, Pure mathematics, Applied Mathematics, Radio Physics (Electronics and EM propagation), Mathematical Physics, and chemistry (one year) with a one hour class in every subject, every single day of the school year, plus a once a week lab in the Physics courses for another few hours, I didn’t have much free time, to study political science or French Literature.
My son has been going to San Fran State U for at least 13 years trying to get some sort of Movie Arts, and Engineering degree. But he is required to waste most of his time doing remedial English classes and tests, because the majority of the students are non English speakers, so everyone; no exceptions, is required to do English before they can graduate, and waste money paying for it.
SF state U is mostly known for its “School of Racism”. Well they use some euphemism like “ethnic studies” or some such; but yes that’s just blatant racism.
Carsten Arnholm says:
August 30, 2013 at 10:34 pm
By that you mean that the Maunder Minimum was a manifestation of a cyclic phenomenon?
W\hat Eddy noted was the absence of cycles, but today we know that the cycle continued anyway [in cosmic rays].
Hang in there, George. Just one more year and they’ll make him a professor!
And he will move out!
#(:))
george e. smith says:
August 30, 2013 at 10:40 pm
Well I only got an ordinary peasant BSc from an ordinary New Zealand University. They give bachelor of Science degrees to people who study science; not Arts,
B.A. in physics is quite common in the U.S. Even Harvard and MIT grant it (but they call it A.B.) In the UK, Oxford grants a B.A. in physics. Just Google “B.A. in physics.”
“Arts” doesn’t mean what you seem to take it to mean, but I’m hard put to say what it means. I see one (non-authoritative) source saying that “arts” have to do with “why,” while “sciences” have to do with “how.” The same or another source says that “arts” in “B.A.” no more refers to “art” than “philosophy” in “Ph.D.” refers to philosophy.
It looks to me like fewer physics and math courses are required for a B.A. than for a B.S.
Also take a look here.
Tom in Florida says: August 30, 2013 at 5:34 pm
Jeez, we just have Bart bow out and up pops Vuk again
Hi Tom
Many years ago I had to attend Communist youth meetings and listen to the same preaching of self appointed old ‘revolutionaries’. Once or twice I summoned enough courage to voice opposite view, got myself into a lot of trouble, and soon as I got my degree I was off.
Here I only bring to your or others attention, what is in the data and may (or you may think not) be of some relevance. Have another look
http://www.vukcevic.talktalk.net/Ap-VI.htm
and decide for yourself if worth your attention.
No, you don’t think so. Fine with me, but I wish you did say so.
If I’m not mistaken the ACRs alternate shapes of peaks from cycle to cycle, flat and sharp. With approximately three such peaks in one phase of the PDO, this provides a mechanism for alternating temperature phases of the PDO, if the energy entering the ocean suffers a cosmic ray effect. I’ve been well assured that this is a low order effect, and so probably, but there it is.
======================
Back to van de Graff: there are insulators and there are insulators. Hard to resist ‘insolators’, but it is distinctly peripheral. Why couldn’t a similar effect be acting to make asymmetrical the hemisphericity of the sunspots, slowly now, slowly?
============
Heh, school was a batch of arts and a degree of technique.
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OK, if the center has no meaning, how can a butterfly flap a wing? The compost heaps and heaves.
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Local explosions in an extremely tenuous plasma (corona) can provoce temperatures from 1,000,000 K and higher?
At about 500 kilometers above the photosphere we find the coldest measurable temperature, about 4400 degrees K. The temperature then rises steadily to about 20,000 degrees K at the top of the chromosphere, some 2200 kilometers above the Sun’s surface. Here it abruptly jumps hundreds of thousands of degrees, then continues slowly rising, eventually reaching 2 million degrees in the corona.
Astronomer Fred Hoyle pointed out that with the strong gravity and the mere 5,800-degree temperature at the surface, the Sun’s atmosphere should be only a few thousand kilometers thick, according to the “gas laws” astrophysicists typically apply to such bodies. Instead, the atmosphere balloons out to 100,000 kilometers, where it heats up to a million degrees or more.
This “reverse temperature gradient,” contradicts every original expectation of the fusion model.
In a gravity-driven universe particles are not hot enough to escape such massive bodies, which (in the theory) are attractors only. And yet, the particles of the solar wind continue to accelerate past Venus, Earth, and Mars.
So what force powers the Solar dynamo and the corona at the same time?
vukcevic says:
August 31, 2013 at 12:10 am
“Here I only bring to your or others attention, what is in the data and may (or you may think not) be of some relevance. Have another look http://www.vukcevic.talktalk.net/Ap-VI.htm
and decide for yourself if worth your attention. No, you don’t think so. Fine with me, but I wish you did say so.”
Vuk, just an attempting to bring a little humor into what has become a rather tiresome thread.
I have looked at all your graphs and am in no position to judge whether they are meaningful or not. I see sometimes they match and sometimes they don’t. What I don’t see is a detailed explanation as to why you are using the formula you devised, what is it based on, what each variable means and if those variables are being applied appropriately. If you have links to that please post them for me. Thanks.
kadaka (KD Knoebel) says:
August 30, 2013 at 3:48 am
Strange, I was certain I was thinking of a single sphere with an intersecting plane, and was getting hung up by thinking about the amounts of mass of the sphere above and below the plane. But obviously you know better what I was thinking than I knew what I myself was thinking.
I don’t doubt that you were thinking of a single sphere with an intersecting plane, but your argument ignored the solar mass below the surface of, and not part of, the earth-mass sphere. That’s the same as mischaracterizing the situation.
I wasn’t thinking in terms of shells, but of the intersecting plane. And yes, I didn’t know exterior shells didn’t count. If I could do the math, I would have come up with the same answers by my approach, the fundamentals were sound.
I don’t see how you’d have come up with it, even if you had not ignored the solar mass I said you ignored. Can you explain how?
I was thinking in more general terms, when a specific simpler approach was available. But what if the object studied was not a sphere, but an ovoid? How would you proceed?
I’d have to integrate over all points on the ovoid shell. With an ovoid, your weight would not be the same everywhere in the interior, as far as I can see.
kim says:
August 31, 2013 at 2:16 am
If I’m not mistaken the ACRs alternate shapes of peaks from cycle to cycle, flat and sharp.
It is the ordinary CGRs that show the alternation of flat and sharp peaks [controlled by the alternating signs of the solar polar fields].
Robertv says:
August 31, 2013 at 4:43 am
Local explosions in an extremely tenuous plasma (corona) can provoke temperatures from 1,000,000 K and higher?
Exactly! Helped along by upwards travelling magnetohydrodynamic waves dissipating in the corona. It is the very thinness of the corona that makes this possible as not much energy in required.
This “reverse temperature gradient,” contradicts every original expectation of the fusion model.
Fusion takes place in the core and has nothing to do with the corona. It is not a ‘fusion model’. It is a ‘fusion fact’.
In a gravity-driven universe particles are not hot enough to escape such massive bodies
If you boil a pot of water, the steam is hot enough to escape the water and rise. In fact, it is gravity that helps the solar wind to escape at supersonic speeds. The physics is the same as in a de Laval Nozzle http://en.wikipedia.org/wiki/De_Laval_nozzle : “As a gas enters a nozzle, it is traveling at subsonic velocities. As the throat contracts down the gas is forced to accelerate until at the nozzle throat, where the cross-sectional area is the smallest, the linear velocity becomes sonic. From the throat the cross-sectional area then increases, the gas expands and the linear velocity becomes progressively more supersonic”. Gravity plays the role of the contracting throat and the reduction of gravity with altitude plays the role of the increasing cross-sectional area.
So what force powers the Solar dynamo and the corona at the same time?
None directly, as the two processes are very different.
Thanks for the correction of my misapprehension, Leif. The mechanism, if it be one, is subtle.
===============
Has the speed and variability of the meridional flow have any relationship with the suns core?
Sparks says:
August 31, 2013 at 6:57 am
Has the speed and variability of the meridional flow have any relationship with the suns core?
Not that we know of, except for the trivial fact that the energy for all solar phenomena ultimately derives from fusion in the core.
From the excerpt ..
..Through removing a systematic center-to-limb effect that was only recently identified, our analysis corrects and improves the previous solar interior meridional flow profile given by Giles (1999) using a similar analysis procedure. ..
—
Dr. S., in the studies I’ve seen on solar differential rotation, they were near correcting for, some sort of limb effect, which caused errors in the calculation of the polar rotation speed of the solar differential rotation. The equatorial rotation speed has been thought to be accurate, whilst the polar rotation speed was found to be askew..
Once they have the correction, will they be able to extrapolate? that back in time, to correct earlier studies?
Also, note..
Voyager 1 at 35 deg. NORTH lat. and at a distance of 120 AU, is in a magnetic highway region (pile up zone).
The magnetic field they are seeing is that coming from the solar southern hemisphere. So are we saying that the magnetic equator is then north of that or where is the magnetic equator way out there?
Then where is the solar field that is produced in the solar northern hemisphere way out there?
Got this info from AGU Fall 2012 SF video at around 10 minutes in. He describes it as being pushed up at that location. Sounding like the dent region moving.
If you copy and paste the link, don’t use the added periods on the end.
From Smoking Frog on August 31, 2013 at 6:23 am:
If you had been following the discussion then you saw the part where that intersecting plane made hemispheres, with the plane then moving outward. Where is this missing mass you speak of there?
Leif and I have completed our frame of reference musings, I see what my problem was there. You cannot even comprehend the one I was trying to use enough to render a competent opinion of what I was showing. Until you do, and can issue a coherent description of what you perceived as an issue, this dialogue is pointless.
Robertv says:
August 31, 2013 at 4:43 am
..So what force powers the Solar dynamo and the corona at the same time?
—
Part of coronal heating IMHO will be found in the interactions of solar wind, fields and plasmas in the ‘Super Halo’ region that extends to 1AU. This would include interactions with the inner planets. We do know that a lot of the geomagnetic storm activity we see at Earth, gets ejected back into the ‘Super Halo’ or back into space during reconnection events. (fountains) This little exclusion boundary out at 1AU is a pretty dynamic portion of the solar system activities..
Carla says:
August 31, 2013 at 8:15 am
Dr. S., in the studies I’ve seen on solar differential rotation, they were near correcting for…
The correction mentioned in the paper is not about differential rotation, but corrects an instrumental artifact specific to the way the instrument works.
The magnetic field they are seeing is that coming from the solar southern hemisphere. So are we saying that the magnetic equator is then north of that or where is the magnetic equator way out there?
The magnetic ‘equator’ is not a plane but a curved surface, basically pictured here http://wso.stanford.edu/gifs/helio.gif as we learned way back in the 1970s: http://www.leif.org/research/HCS-Nature-1976.pdf and http://www.leif.org/research/A%20View%20of%20Solar%20Magnetic%20Fields,%20the%20Solar%20Corona,%20and%20the%20Solar%20Wind%20in%20Three%20Dimensions.pdf
The latitudinal extent of the wavy surface is basically determined very close to the Sun. http://www.leif.org/research/On-Becoming-a-Scientist.pdf Slides 10-16 show how magnetic fields from one hemisphere push into the other, so even at northern latitudes we can see fields originating from the southern hemisphere. The ‘bending’ takes place in the outer corona, e.g. as shown in Figures 1 and 2 of the Three Dimensions link.