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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Leif Svalgaard says:
August 30, 2013 at 9:16 am
Jim G says:
August 30, 2013 at 9:09 am
“No, because gravity is zero at the center.”
Is this per general relativity as well as Newtonian gravity?
“I think we are way off, off, off topic with little return for the effort expended.”
Thank you in any event for your responses.
Jim G says:
August 30, 2013 at 9:17 am
Length contraction and time dilation are supposed to occur all along the way just increasing as velocity and/or gravity increase
Einstein’s point was that in free fall there is no gravity hence no time dilation or length contraction so none of those effects for an observer falling towards the singularity.
Leif Svalgaard says:
August 29, 2013 at 7:47 pm
“You are a victim of that, but don’t know it [in good D&K style]”
No, you are the victim of it. The methodology I speak of is not mine. It has been used extensively and successfully in uncountable applications where the mathematical framework is <i<precisely the same. It is applicable here, trivially so, to someone who works with the theory almost every day, churning out products which actually work to paying customers.
You are not familiar with it and so, in true D&K style, you dismiss it. That’s your loss, and now you’ve backed yourself into a corner. I expect that kind of chest-thumping bravado from a kid fresh out of school. You have no excuse for your immaturity.
Greg Goodman says:
August 30, 2013 at 8:29 am
Thanks. Good comments. But Leif has backed himself into a corner. It’s no longer about science, and hasn’t been for quite some time. It’s about establishing alpha supremacy. Very sad.
Leif Svalgaard says:
August 30, 2013 at 9:29 am
Jim G says:
August 30, 2013 at 9:17 am
Length contraction and time dilation are supposed to occur all along the way just increasing as velocity and/or gravity increase
“Einstein’s point was that in free fall there is no gravity hence no time dilation or length contraction so none of those effects for an observer falling towards the singularity”
There are experiments that indicate that time dilation has been measured on orbiting satelites in free fall and I have heard of this before. But then that could be due to velocity.
The angular momentum theory makes much more sense then what this latest study is trying to convey.
The angular mometum theory if one uses past history has shown that when the planets exert a certain amount of angular momentum upon the sun due to their orbital relationship about the sun, that the sun has entered either a very active period or inactive period.
Geoff Sharp has used this theory to make his solar forecast which have been quite accurate.
The study that was done really is saying nothing new, it is just an expansion on what they had already thought. The angular momentum theory gives a cause and an effect, this latest theory can not explain why the sun does what it does ,it just says it does what it does.
IT HAS NO CAUSE FOR WHAT THE SUN DOES.
Bart says:
August 30, 2013 at 9:39 am
No, you are the victim of it. The methodology I speak of is not mine. It has been used extensively and successfully in uncountable applications
So is a hammer, but that does not mean it is the proper tool for everything.
now you’ve backed yourself into a corner. I expect that kind of chest-thumping bravado from a kid fresh out of school. You have no excuse for your immaturity.
I’m in a very comfortable corner. And no excuse is needed. I repeat: your analysis [no matter how well executed and how much your customers pay for your expertise] is not applicable to the real sun, nor is it universally applicable to every phenomenon in the Universe.
It’s about establishing alpha supremacy. Very sad.
Your comments show who is seeking alpha supremacy [you, in case you didn’t get it]. And it is indeed sad, but such is life. You are not alone.
Jim G says:
August 30, 2013 at 9:40 am
There are experiments that indicate that time dilation has been measured on orbiting satelites in free fall and I have heard of this before. But then that could be due to velocity.
The issue is ‘time dilation’ with respect to whose time? Time dilation is a difference of elapsed time between two events as measured by observers either moving relative to each other or differently situated from gravitational masses. For a single observer falling into a singularity there is no time dilation, because there is no other observer to compare with. Now, for an observer outside of the horizon watching you falling towards to hole, the situation is different: he would see you slow down as you approach the horizon and actually never crossing it [light from you would also be increasingly red-shifted so he can eventually not see you]. The difference in experience is why the theory is called ‘relativity’.
Jim G says:
August 30, 2013 at 9:40 am
Not sure what you guys are discussing, but yes, time dilation occurs on orbiting satellites. The higher your orbit, the faster your clock relative to one on Earth. However, at circular orbit altitude of approximately 1.5 times Earth radius and below, your orbital speed starts to slow down your clock more than the weaker gravity speeds it up, and time runs faster on the Earth.
GPS satellite clocks are corrected by the appropriate factor so that they will measure time as it would be on the surface of the Earth. See chapter 18 “Introduction to Relativistic Effects on the Global Positioning System” here.
Oops. Here.
Errata: Should have said “circular orbit radius of approximately 1.5 times Earth radius” or “circular orbit altitude of approximately 1/2 times Earth radius.”
Call me simple ,but I want predictions based on these theories, not just theory. Back it up with prediction.
Salvatore Del Prete says:
August 30, 2013 at 10:30 am
Call me simple ,but I want predictions based on these theories, not just theory. Back it up with prediction.
1) they are measurements, not theories.
2) there is theory interpreting the data, I mention one here:
Leif Svalgaard says:
August 29, 2013 at 10:09 pm
“The models qualitatively explains the observed synchronization between the polar magnetic field strength and the sunspot number”
3) there are succesful predictions based on the polar magnetic field, e.g.
http://www.leif.org/research/Cycle%2024%20Smallest%20100%20years.pdf
4) once the new polar field has been established [in about three years time] we can make a good prediction for cycle 25.
So, there you have it. Alternatively, you can use Bart’s ‘model’ to get your predictions 🙂
Greg says
http://wattsupwiththat.com/2013/08/29/a-new-understanding-of-the-solar-dynamo-published/#comment-1403761
Well said. Agreed!
\
Leif says
And all very wrong.
Henry@Leif
You are such a fraud. For one thing, why don’t you stop talking to your alter ego’s on this thread as if you were arguing with yourself (perhaps to attract high visiting numbers?)
Do you honestly think that we don’t see through you?
Leif says
) there are succesful predictions based on the polar magnetic field, e.g.
http://www.leif.org/research/Cycle%2024%20Smallest%20100%20years.pdf
4) once the new polar field has been established [in about three years time] we can make a good prediction for cycle 25.
Henry@Leif
We did look at that before, remember?
It seems you are admitting now that 2016 is an important date,
as was 1972.
http://blogs.24.com/henryp/2012/10/02/best-sine-wave-fit-for-the-drop-in-global-maximum-temperatures/
It must be something to do with the planets? Or what?
In 2016 we will be at deep end of the polar fields, both sides, and in 1972, if we go back, there must be a dead end stop (at the top/bottom)
Why don’t you put those results of the +/- polar field into binomials (parabolic/hyperbolic) and give us your comment as to why what happens (if we observe the best fit)
If you give me the data, I can also do it myself, but I don’t have time, for some time.
Leif Svalgaard says:
August 30, 2013 at 10:13 am
“…you, in case you didn’t get it…”
Well, I regret our discussions have degenerated into mutual abuse for whatever reason, and whomever is more or less at fault. I am completely aware that your experience in solar dynamics is vast and knowledgeable, which is why I for one would never call you incompetent. But, my experience in matters dynamical and mathematical is similarly vast, and successful, I might add. Of course, I can just say that, but you don’t know me from Adam, and are justifiably cautious about accepting my input. Unfortunately, I am in a position where my doubts about AGW could materially affect my company’s ability to gain contracts, and I being just one person in the organization whose views are not widely shared within it, would be in the position of harming innocent colleagues and friends.
I would hope that my demonstration of a variety of skills would convince you that I have at least some heft to my claims. In my view, you are looking at the trees, but I am attempting to direct your attention to the forest.
This little olive branch will probably gain me nothing more than additional abuse. At least, that is how it has gone down in the past when I have made overtures. You appear to have a strong inclination to nurse grudges. This is not a very constructive policy. By your response, I will let others judge you. I have offered you my “hammer”. It is a very good hammer, which has seen extensive use. It could help you nail the boards together, if you ever tire of your tongue and groove work.
Leif Svalgaard says:
August 30, 2013 at 10:40 am
“Alternatively, you can use Bart’s ‘model’ to get your predictions”
My “model” is still quite complicated. It is not merely adding a bunch of sinusoids, though with light damping, that may not produce a completely off-base result. I believe Vuk has done so with some inarguable success. My model assumes the quasi-sinusoids arise from lightly damped modes, which represent a truncated modal expansion of a solution to your partial differential equations. These modes are driven by wideband noise, so any prediction from their current state will diverge over time.
A Kalman Filter could be devised for this system. It can be trained with past measurements, and then projected into the future with quantifiable error bars from the Kalman Filter covariance propagation.
I don’t know why but that word “singularity” tickles me. Maybe it reminds me of words like “jocularity”. It is such a funny rolling tongue word. Speaking of fun, those two boys I spoke about on the “eclipse” thread used to end their writing time with me with spelling challenges. We would use a collegiate spelling dictionary to challenge each other on spelling unusual scientific words with lots of Latin components (don’t they all have lots of Latin components?).
“My model assumes the quasi-sinusoids arise from lightly damped modes, which represent a truncated modal expansion of a solution to your partial differential equations.”
Such an approach is very general. Bounded partial differential equations tend to such solutions. The methodology has been employed successfully in a wide variety of applications, including structural vibrations, fluid transport, electrical power subsystems, and electronic devices. There is no reason it should not be applicable to solar dynamics.
Bart I would be interested in the areas you agree with Leif and the areas you disagree. Thanks.
Bart says:
August 30, 2013 at 11:09 am
Well, I regret our discussions have degenerated into mutual abuse for whatever reason
There is no doubt about your vast expertise in what your do. The issue is whether it is applicable, and I think not.
In my view, you are looking at the trees, but I am attempting to direct your attention to the forest.
Your view is yours, but does not reflect where my attention is, which is very much on the forest.
This little olive branch will probably gain me nothing more than additional abuse.
You are presumptuous.
I have offered you my “hammer”. It is a very good hammer, which has seen extensive use.
In science we judge such statements by further experiments, so apply your hammer on this time series and show the result. This is a simple ‘put up or shut up’ test, and should not be construed as anything else: http://www.leif.org/research/Ap-1844-now.xls . The data are in column D as a function of time in column C.
About ‘incompetence’: I am a very incompetent violin player [and many other things too], but that does not carry any stigmas for me. And you are a very incompetent solar physicist, and that should not carry any stigmas for you either.
Bart says:
August 30, 2013 at 11:16 am
There is no reason it should not be applicable to solar dynamics.
The shoe is on the other foot. One has to show that it is applicable. Now, people have tried Kalman filter techniques from time to time in the hope that they might work, but with generally poor results. Here are some examples: http://sidc.be/sunspot-index-graphics/sidc_graphics.php
Bart says:
August 30, 2013 at 11:16 am
There is no reason it should not be applicable to solar dynamics.
Have a look at http://www.leif.org/EOS/Lomb-Sunspot-Cycle-Revisited.pdf
and comment on that. Nick Lomb is by most people in my field considered to be competent in signal analysis [even has a well-known technique named after him, http://en.wikipedia.org/wiki/Least-squares_spectral_analysis ]
Leif’s chart of the ap index since 1844 shows how strong it has been in comparisome to post 2005 ,and shows a more or less active sun, with no real prolonged solar quiet periods. It shows a more or less a steady rhythmic cycle in solar activity although strong.
Hence the correlation between solar activity and climate throughout that time period is obscure.
In contrast let us see what might happen with an ap index sub 5 year after year after year, which very likely occurred during the Maunder /Dalton prolonged solar minimums which in turn were associated with a reduction in global temperatures.
Going forward there is a good chance we could see the ap index average below sub 5 once again.
I should have said ap index sub 5 year after year going forward.
Leif Svalgaard says:
August 30, 2013 at 11:35 am
“This is a simple ‘put up or shut up’ test…”
Someday, when I have the time, I will take up the challenge. I will mark this page and the reference to the data you have kindly provided.
For now, I think I will depart on this relatively high and amicable note. Good hunting to you, Dr. Svalgaard.
HenryP says:
August 30, 2013 at 11:06 am
It seems you are admitting now that 2016 is an important date
absolutely, my eldest granddaughter turns 21.
Janice, IMHO there is no room for color commentary and soft spoken “nice” in scientific discourse. I know whereof I speak. I had to scrub my manuscript of all such brushstrokes. Cold hard facts, keeping feet to the fire of demonstrated plausible and unvarnished mechanism based on unvarnished statistical analysis of hard data, and cold hard feedback is the only way we can stear clear of the same mistakes that invade AGW hysteria among even those with science credentials. I prefer blunt cutting discourse. It leads to improved understanding much quicker than mamby pamby politeness ever could accomplish. That we could pepper AGW blogs with the likes of Leif would end this expensive madness way sooner than what discourse we currently have.
Salvatore Del Prete says:
August 30, 2013 at 11:53 am
In contrast let us see what might happen with an ap index sub 5 year after year after year, which very likely occurred during the Maunder /Dalton prolonged solar minimums
Modern data shows that Ap depends on the interplanetary [i.e. solar] magnetic field, B, [Ap ~ BV^2, where V is solar wind speed]. B is a main factor in modulating cosmic rays. If Ap is low year after year, there will be no modulation of cosmic rays, yet during the Maunder Minimum the cosmic ray modulation was strong [even stronger than the past several cycles]. So, that argues for Ap not being low, year after year.
Pamela Gray says:
August 30, 2013 at 12:02 pm
Janice, IMHO there is no room for color commentary and soft spoken “nice” in scientific discourse.
Science is a blood sport. And must be.