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.
=================================================================
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 31, 2013 at 8:39 am
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
But is there immediately picked up by the supersonic wind and swept further out away from the Sun. The stuff does not go back to the Sun to heat the corona.
In that AGU video above about the Voyager 1 findings, “the wind has been deflected and pushed up to the northern hemisphere, forming a layer, on the very outer edges of the heliosphere, right next to the heliopause which is the boundary..”
Coincidently, that second stream of GCR they have found, generally speaking comes in from the dent location region in the southern heliospheric hemisphere. Where as the other GCR stream is coming from the Sco Cen association in the headwind direction. This may be another indicator (if GCR gyrate along interstellar field lines) that the heliosphere is located at a filamentary boundary region of sorts.
Carla says:
August 31, 2013 at 9:32 am
In that AGU video above about the Voyager 1 findings, “the wind has been deflected and pushed up to the northern hemisphere, forming a layer, on the very outer edges of the heliosphere, right next to the heliopause which is the boundary..”
I don’t know how many times it is necessary to repeat this: the deflection takes place in the corona, very close to the Sun, within 5 solar radii from the surface. Then the solar wind transports that deflected plasma out to the heliopause.
Now I’m thinking they are looking the wrong way in trying to find the direction of the interstellar magnetic field orientation or which way is the interstellar field going? Maybe coming from the second GCR stream that interstellar field is running parallel to the solar field.
Carla says:
August 31, 2013 at 9:32 am
a filamentary boundary region of sorts.
The solar wind and interstellar space are full of filaments. Some people describe it as ‘magnetic spaghetti’ http://tri-lab.lanl.gov/index.php/energy-security/85-understanding-solar-wind-structure or http://adsabs.harvard.edu/abs/2011AGUFMSH41C..06B
Carla says:
August 31, 2013 at 9:39 am
Now I’m thinking they are looking the wrong way in trying to find the direction of the interstellar magnetic field orientation or which way is the interstellar field going?
scientists are not morons. be assured that they think of it in all possible and plausible ways. A simple explanation is that the spacecraft are not yet really in true interstellar space and are simply sampling the solar wind field.
Leif Svalgaard says:
August 31, 2013 at 9:37 am
—
Are you referring to the origination location of the HCS and the kinks and waves we see propagating outwards even out to 100 AU start at about 5 solar re above the solar surface in the corona? This is caused by deflection?
Do GCR gyrating along field lines create waves, are waves turbulence?
And could the heliopause be analogous to Earth’s magnetic pause in its ‘inward and outward’ daily fluctuations. Do these motions also produce waves?
One more time..
“The Futures so Bright” by Timbuk 3
“a peeping tom techy with X-Ray eyes”.
One last question..heh
Does the so called ‘Super Halo’ out to 1AU also have a magnetic pause, that fluctuates inward and outward, that we do not, have not ?? looked for with OUR star? Boy that changes everything.
From the outside looking in today..
So.. can we say that within these counter rotating, sub surface meriodonal flows we now see at the sun, are where streamers and pseudo streamers are formed? And have the pseudo streamers (the ones with closed field lines/no escape of solar wind) been dominate throughout cycle 24 and generally on the increase within the counter rotating cells below the surface? Are the polar rotations speed more slower this cycle 24 than the last and before that etc..?
And would all that make the HCS wavy also?
rant over
With all this rotational business we might also say solar differential rotation, can be hemispheric. In that if let’s say the oh Northern hemisphere has more active regions, sunspots, the Northern hemisphere will be rigid from the active regions and rotate slower than the southern. This doesn’t take into account the polar rotation. But would affect meriodonal flow and hemispherically too..
wow rotation in the galaxy, in so many places, doing so many different things, makes me kinda dizzy..
Just one more.
If the polar rotation of the sun is less affected by active regions, sunspots etc. because of the benefit of a surface area to limb effect of rotation, what role do pseudo streamers, with no solar wind escape, have on slowing the polar rotation? Like the pseudo streamers just need one more little twist..
Carla says:
August 31, 2013 at 10:09 am
Are you referring to the origination location of the HCS and the kinks and waves we see propagating outwards even out to 100 AU start at about 5 solar re above the solar surface in the corona? This is caused by deflection?
Yes, near the Sun the Sun’s polar magnetic field is strong enough to deflect and bend the solar wind; further out, the wind just expands radially and ballistically [like bullets shot from a gun on the Sun]
Do GCR gyrating along field lines create waves, are waves turbulence?
No, they don’t. They are like gnats on the back of an elephant.
And could the heliopause be analogous to Earth’s magnetopause in its ‘inward and outward’ daily fluctuations.
In both cases [but don’t take the analogy too far] the variations are caused by the central body: the tilted Earth rotating [and changing polarity every million years or so] and the wavy HCS also rotating [and the solar polar fields changing polarities].
Do these motions also produce waves?
Some, but the solar wind blows everything outwards.
Carla says:
August 31, 2013 at 10:19 am
Does the so called ‘Super Halo’ out to 1AU also have a magnetopause
You must be referring to the energetic electron flux. In addition to the solar wind there are also Solar Energetic Particles. Those are often emitted in ‘bundles’ [from from flares, for example] or narrow streams. A bundle has a ‘core’ in the middle with particles surrounded by a sheath or halo around the core. Spacecraft at 1 AU have observed those halos and at times even more energetic ones – the ‘superhalos’. So, the halo in a given stream is not surrounding the Sun and is present at all distances [nothing special about 1 AU – which is just where the spacecraft happened to be]
Carla says:
August 31, 2013 at 10:28 am
can we say that within these counter rotating, sub surface meridional flows we now see at the sun, are where streamers and pseudo streamers are formed?
No, the magnetic field that erupts on the surface is formed down there. The streamers and pseudo-streamers are formed in the corona as the plasma adjusts itself to the magnetic fields.
etc?
Basically no 🙂
Carla says:
August 31, 2013 at 10:32 am
would all that make the HCS wavy also?
the pattern of the magnetic field on the surface and its simplification [as closing loops don’t reach up far enough] in the corona make the waves in the HCS
Carla says:
August 31, 2013 at 10:47 am
wow rotation in the galaxy, in so many places, doing so many different things, makes me kinda dizzy..
Each body rotates in its own way, not really governed by the rotation of the Galaxy.
Science is a blood sport.
And mustIt need not be.(editing Dr. Svalgaard at 12:05pm, 8/30)
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Vukcevic, I’m so glad that you made it out of that Communist hellhole. It must be tough to watch the free world so blithely hand over its liberties to the Envirostalinists.
Carla says:
August 31, 2013 at 10:57 am
what role do pseudo streamers, with no solar wind escape, have on slowing the polar rotation?
None. If you throw a rock up in the air and it falls down again, that act does not slow the Earth’s rotation. Also, the corona is exceedingly tenuous. I noticed up-thread that the pressure of all the stuff in the corona [incl. pseudo-streamers] on the surface is like the pressure under a foot of a spider.
Janice Moore says:
August 31, 2013 at 11:01 am
“Science is a blood sport.”
It need not be.
It must be. There is only one truth [as we see it, of course]. We don’t send two spacecraft to Mars using two contradictory theories of gravity, just because we want to be nice to both camps of proponents.
Leif Svalgaard says:
August 30, 2013 at 6:39 pm
“If there is, as you suggest, a direct relationship, then you should find the same two ‘cycles’ beating against each other.”
Not necessarily. In an AM radio, you have the carrier cycle beating against the amplitude signal. When the signal is rectified and low pass filtered, you retrieve the amplitude signal with the carrier effectively stripped away. Something similar, I believe, would be the likely effective mechanism. Not necessarily the only mechanism affecting temperature, mind you, but one of them. Fed through a system with dominant observed resonances, particularly that associated with the ~60 year observed cycle in the data, this could potentially account for the lion’s share of what has been observed over the past century+.
Yes, I have not proved it. Another analysis waiting from my attention someday. Or, hopefully someone else’s. But, until it has been thoroughly and appropriately investigated, I would caution against making firm conclusions. The heat energy does ultimately have to come from the Sun, after all.
Pamela Gray says:
August 30, 2013 at 8:16 pm
“These moving, not well mixed, dynamic pools and waves are not cyclical nor do the effects they cause cancel each other out over time.”
This is begging the question. What makes those pools dynamic?
Bart says:
August 31, 2013 at 11:11 am
I would caution against making firm conclusions.
That works both ways. We make conclusions of what is believed to be known at this time. And no conclusion in science is ever ‘firm’.
until it has been thoroughly and appropriately investigated
I represent to you that it HAS been so investigated, by hundreds of people. It is still debated for the simple reason that the case for the Sun being a major driver is weak and not compelling enough to be actionable.
Leif Svalgaard says:
August 31, 2013 at 11:20 am
“That works both ways. “
Agreed.
“I represent to you that it HAS been so investigated, by hundreds of people.”
So has CAGW. How’s that working out?
Bart says:
August 31, 2013 at 11:38 am
“I represent to you that it HAS been so investigated, by hundreds of people.”
So has CAGW. How’s that working out?
Lemme see: 97% of scientists think pretty well. But, they, obviously, do not have your hammer 🙂
The point is that you can prove absolutely nothing with signal analysis and statistics. The physics has to be understood. An analogous case is that of whether the Sun is the cause of geomagnetic storms. It took 150 years to figure out what the physics is and data analysis of the geomagnetic record did not help one bit.
Several nights ago, I came across a graph from SIDC that shows the international sunspot number in a monthly format from 1950 to the present. It shows the trend in excess sunspot numbers with either the north hemisphere leading the south, or the south hemisphere leading the north. The graph shows that from slightly before 1950 up until 1972 the north predominates. Then from 1972 till 1974 the south plays a strong role, which is followed by the north resuming the lead until 1980. After 1980 and all the way till 2008, the south dominates in the excess ssn count. Since 2008 the north is now back on top.
The ‘north’ Sun from 1950 till the late 70s led the Earth through a slight cooling period. Then the ‘south’ Sun has a strong show between 1972 through 1974. Is this the beginning of the warming which first shows up in 1977. The ‘south’ Sun,1980 till 2008, leads the Earth through a noticeable warming. Now we are back into a ‘north’ Sun and the Earth has seen a slight cooling since 2006/07. So, why is it that the IPCC doesn’t consider the Sun as having a greater affect. How can this graph correspond so closely to the warming and cooling cycles of the Earth? I was looking at Bob Tisdale,s latest post and his global temp graph. The SIDC graph appears to have good correlation with his graph. Even some of the brief changes, 1 to 2 years of a large change, in excess sunspot numbers seem to show up on Bod Tisdale,s graph.
Here is a link to the graph…http://sidc.oma.be/sunspot-index-graphics/wnosuf.php
Leif Svalgaard says:
August 31, 2013 at 11:46 am
“Lemme see: 97% of scientists think pretty well.”
I assume that is tongue-in-cheek.
“The point is that you can prove absolutely nothing with signal analysis and statistics.”
I disagree.
“The physics has to be understood.”
Really? You disagree with this fellow?
“Anyone who says that they understand Quantum Mechanics does not understand Quantum Mechanics”
-Richard Feynman
“The physics has to be understood… It took 150 years to figure out what the physics is and data analysis of the geomagnetic record did not help one bit.”
IOW, you have to understand the physics in order to understand the physics. You realize this is a tautology?
Bart says:
August 31, 2013 at 12:08 pm
I assume that is tongue-in-cheek.
I assume ‘So has CAGW. How’s that working out?’ was too. At least it was irrelevant.
“The point is that you can prove absolutely nothing with signal analysis and statistics.”
I disagree.
Well, a snake-oil salesman would also disagree that this medicine is useless.
“The physics has to be understood.”
Really? You disagree with this fellow? “Anyone who says that they understand Quantum Mechanics does not understand Quantum Mechanics”
Yes, because you misuse or don’t know the word ‘understand’ in this context. The physics is the precise rules of quantum mechanics. What Feynman was referring to was ‘understanding’ in terms of our usual experience which is something completely different.
“The physics has to be understood… It took 150 years to figure out what the physics is and data analysis of the geomagnetic record did not help one bit.”
IOW, you have to understand the physics in order to understand the physics. You realize this is a tautology?
Nonsense. You have to understand the physics in order to understand the phenomenon. No tautology, just plain talk.
Leif Svalgaard says:
August 31, 2013 at 12:17 pm
“At least it was irrelevant.”
It was completely relevant. Stating that hundreds of people have worked on a problem gives no indication of the quality of their work.
“The physics is the precise rules of quantum mechanics.”
No, those are merely rules. Rules can be derived empirically. How accurate they are often depends on the understanding which goes into them. But, often, such rules are accurate enough for the intended application. Quantum mechanics is an example in which there is really only hazy understanding of the physics, but for which the rules which were worked out perform exceedingly well. The inverse square law of gravity is another example of such rulemaking which was “good enough” for widespread application. The Lorenz transformation preceded understanding how it came about, and was derived empirically.
“You have to understand the physics in order to understand the phenomenon.”
But, understanding is often not necessary to make abundant use of empirically derived knowledge. See above.
Our point of contention should not be whether such rules can be determined with or without in-depth understanding. Clearly, they can. The question is how accurate and useful they can be without that level of understanding. Your claim is that they cannot be very accurate. I claim they can, but proof of my contention is, as we have agreed I think, TBD.
Leif Svalgaard says:
August 31, 2013 at 10:57 am
Do GCR gyrating along field lines create waves, are waves turbulence?
No, they don’t. They are like gnats on the back of an elephant.
—
Well then according to Voyager 1, instead of the gnats gyrating around the magnetic field like they had been, they are NOW running parallel.
Carla says:
August 31, 2013 at 10:19 am
Does the so called ‘Super Halo’ out to 1AU also have a magnetopause
You must be referring to the energetic electron flux. In addition to the solar wind there are also Solar Energetic Particles. Those are often emitted in ‘bundles’ [from from flares, for example] or narrow streams. A bundle has a ‘core’ in the middle with particles surrounded by a sheath or halo around the core. Spacecraft at 1 AU have observed those halos and at times even more energetic ones – the ‘superhalos’. So, the halo in a given stream is not surrounding the Sun and is present at all distances [nothing special about 1 AU – which is just where the spacecraft happened to be]
—
This ‘Super Halo’ out to 1AU is a consistent and persistent. Whether there be solar cycle activity or not.
It is a hard read though..
QUIET-TIME INTERPLANETARY ∼2–20 keV SUPERHALO ELECTRONS AT SOLAR MINIMUM
Received 2012 May 15; accepted 2012 June 3; published 2012 June 18
http://sprg.ssl.berkeley.edu/adminstuff/webpubs/2012_aj_lL23.pdf
Linghua Wang1,2, Robert P. Lin2,3,4, Chadi Salem2, Marc Pulupa2, Davin E. Larson2,
Peter H. Yoon4,5, and Janet G. Luhmann2
Abstract
..The density of superhalo electrons
appears to show a solar-cycle variation at solar minimum, while the power-law spectral index ã has no solar-cycle
variation. These quiet-time superhalo electrons are present even in the absence of any solar activity—e.g., active
regions, flares or microflares, type III radio bursts, etc.—suggesting that they may be accelerated by processes such
as resonant wave–particle interactions in the interplanetary medium, or possibly by nonthermal processes related
to the acceleration of the solar wind such as nanoflares, or by acceleration at the CIR forward shocks.
1. INTRODUCTION
The solar wind electron population near 1 AU is observed
to be dominated by a thermal (∼10 eV) Maxwellian core
(∼90%–95% of the density), with ∼5%–10% in a much hotter
(∼50 eV) halo/strahl whose velocity distribution functions
(VDFs) ….. fit to a Maxwellian/Kappa distribution.
The highly anisotropic, antisunward
field-aligned strahl results from the escape of thermal
electrons from the hot (∼106 K) solar corona (e.g., Feldman
et al. 1975; Salem et al. 2007) that carries heat flux outward,
while the isotropic halo may be due to scattering of the strahl
(e.g., Montgomery et al. 1968; Feldman et al. 1975; Rosenbauer
et al. 1977; Pilipp et al. 1987; Pierrard et al. 2001). High sensitivity
measurements covering the entire range from a few eV
up to ∼400 keV by the 3D Plasma & Energetic Particle (3DP)
instrument on the WIND spacecraft (Lin et al. 1995) discovered
a suprathermal electron component, denoted the “superhalo”,
that dominates above ∼2 keV (Lin 1997, 1998), with a powerlaw
(dJ/dE ∼ E−β with β ∼ −2.5) spectrum extending to
>100 keV, and a nearly isotropic angular distribution.
This superhalo appears to be present at all times, even in the
absence of solar or interplanetary activity, and thus appears to
be the electron counterpart of the power-law-tail suprathermal
ions above solar wind and pickup ion energies that are observed
throughout the heliosphere at all the times (e.g., Gloeckler 2003;
Fisk&Gloeckler 2006). At present, the origin of superhalo electrons
is unknown……….