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
Salvatore Del Prete says:
August 30, 2013 at 9:57 am
The angular momentum theory makes much more sense then what this latest study is trying to convey.
another example of how simplistic musing crowds out real science. The AM ‘theory’ violates the laws of Nature: http://www.leif.org/EOS/Shirley-MNRAS.pdf
Leif Svalgaard says:
August 30, 2013 at 11:53 am
Have a look at http://www.leif.org/EOS/Lomb-Sunspot-Cycle-Revisited.pdf
Nick Lomb concludes: “This study confirms the structure of the sunspot time series demonstrated in paper 1: a stable 11-year periodicity (the Schwabe cycle) that is amplitude and phase modulated by the long-term periodicities discussed above. This clearly implies that a clock mechanism must exist within the Sun for the 11-year periodicity to persist in the solar data as was first suggested by Dicke [10]. Modern theories provide a possible clock mechanism in the conveyor-belt-like meridional circulation between high polar latitudes and the equator. In the Babcock-Leighton models of Charbonneau and Dikpati [11] and [12] remnant magnetic flux from decaying sunspots is transported away from the equator by meridional circulation towards the poles generating the poloidal field of the following cycle. This field is transported to the base of the convection zone where shearing by differential rotation leads to a new toroidal field at low latitudes. Buoyant flux tubes rise to the surface as sunspots. In this way the meridional circulation provides the clock regulating the 11-year cycle and maintaining its continuity. The models predict fluctuations in the meridional circulation and these fluctuations have been observed with the Michelson Doppler Imager on board the SOHO spacecraft [13]. However, according to Charbonneau and Dikpati [11] the meridional circulation can still act as a clock for most of their simulations exhibit ‘good phase locking, in the sense that their cycle periods rarely depart for more than a few consecutive cycles from their average value’. Moreover, the models also reproduce the amplitude-duration anticorrelation that is related to the amplitude-phase relationship discussed in this paper”
Thus connecting with the topic of this thread.
During the Maunder Minimum based on C14, and beryllium data which are sensitive to galactic cosmic rays ,cosmic rays increased substancially during the Maunder Minimum.
Low ap values are associated with increases in cosmic rays, because low ap values occur in conjunction with a low solar wind and low sunspot count over the long run.
That proves the ap index was low , bu tin addition studies show the aa index was in the range of 2or 3 during the Maunder Minimum.
I have many studies showing this to be the case.
Salvatore Del Prete says:
August 30, 2013 at 12:37 pm
That proves the ap index was low , but in addition studies show the aa index was in the range of 2 or 3 during the Maunder Minimum.
You are not paying attention [but links to studies that peddle 2 or 3 would be welcome]. The modulation of cosmic rays depends on B [and therefore on ap], and the modulation during the Maunder [and Spoerer] minima was as strong as today. The background level is much more dependent on unknown factors, such as the climate itself which exerts significant influence on the level of comic rays.
From Leif Svalgaard on August 30, 2013 at 12:05 pm:
Reference: http://wattsupwiththat.com/2010/05/29/leif-svalgaard-on-the-experience-of-peer-review/
Geomagnetic Activity and the Solar Wind During the Maunder …
adsabs.harvard.edu/full/1998ASPC..140..437C
by EW Cliver – 1998 – Cited by 50 – Related articles
We followed the approach of Feynman & Crooker (1978) to relate the 6.9-7.5 nT range of 11 during the Maunder Minimum to solar wind parameters for …
“”””””……kadaka (KD Knoebel) says:
August 29, 2013 at 9:06 pm
For the lovers of Geomagnetic Cycles:
Earth’s center is out of sync
May 13, 2013
(Phys.org) —We all know that the Earth rotates beneath our feet,
Well it sure as hell isn’t rotating beneath my feet; that would really hurt having the earth whizz under my feet at 1,000 nautical miles per hour (on the equator).
It would also wear out my shoes in nothing flat.
The above supports all of my contentions.
Leif you are in denial.
That is okay live and learn.
This decade will prove you to be wrong on all counts.
Geomagnetic Activity and the Solar Wind During the Maunder …
adsabs.harvard.edu/full/1998ASPC..140..437C
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by EW Cliver – 1998 – Cited by 50 – Related articles
SAO/NASA ADS Astronomy Abstract Service. Syrwptic Solar Physics ASP Conference Series, Vol.
“”””””…….kadaka (KD Knoebel) says:
August 29, 2013 at 8:47 pm
From Leif Svalgaard on August 29, 2013 at 7:47 pm:
But on the Sun, in the example, there would be so much mass overhead, that would also exert gravitational forces, that I cannot see how it would still sum to 29 times Earth
The mass overhead doesn’t matter. Newton proved that.
……………………………
And Newton proved it doesn’t matter? It has been awhile since I got my BA in Physics, that did not get used. Perhaps I forgot it. Got a link to an explanatory text?……..”””””””
How on earth does one get a BA in Physics ??
I can see how one might get a BA in that globally important, Indonesian Tribal Dance; or
Rural Poetry of Lapp-land. But Physics; since when did that become an art form ??
AA Index
The aa index is a measure of the disturbance level of the Earth’s magnetic field based on magnetometer observations at two nearly antipodal stations: Hartland observatory in the UK and Canberra observatory in Australia. The following figure shows the aa index since 1868. [http://roma2.rm.ingv.it/en/themes/23/geomagnetic_indices/24/aa_planetary_index]
A NOAA National Geophysical Data Center website states “the overall level of magnetic disturbance from year to year has increased substantially from a low around 1900 Also, the level of mean yearly aa is now much higher so that a year of minimum magnetic disturbances now is typically more disturbed than years at maximum disturbance levels before 1900.” [bold emphasis in original] The following figure is from that website. [http://www.ngdc.noaa.gov/stp/geomag/aastar.html]
The following figure shows the yearly average aa index along with vertical dashed lines indicating the solar cycles, for 1844 – 1997 [http://www.ips.gov.au/Educational/3/1/4]
AA Relationship to Temperature
A 1998 paper (Cliver et al, “Solar variability and climate change: Geomagnetic aa index and global surface temperature”, Geophysical Research Letters, Vol.25, 1998) states: “During the past ~120 years, Earth’s surface temperature is correlated with both decadal averages and solar cycle minimum values of the geomagnetic aa index. The correlation with aa minimum values suggests the existence of a long-term (low-frequency) component of solar irradiance that underlies the 11-year cyclic component. Extrapolating the aa-temperature correlations to Maunder Minimum geomagnetic conditions implies that solar forcing can account for ~50% or more of the estimated ~0.7-1.5°C increase in global surface temperature since the second half of the 17th century.” [http://ruby.fgcu.edu/courses/twimberley/EnviroPhilo/Cliver.pdf]
The following figure is from the above paper showing “Comparison of solar cycle minimum values of the geomagnetic aa index(aamin) and () from 1880-1990”
The same paper states: “The correlation we find between the aa baseline and terrestrial surface temperature suggests the existence of a long-term (low-frequency) component of solar irradiance that tracks the average level of geomagnetic (sunspot) activity. In this view, the absence of pronounced 11-year temperature fluctuations is attributed to the damping effect of the thermal inertia of the oceans.”
The following figure shows the Hadley Climatic Research Unit global average
I subscribe to Cliver and the like and not to your opinoins Leif . Time will tell who is correct and who is wrong.
Their are countless studies similar to the few I posted which refute all that Leif tries to convey.
End of story.
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
Salvatore Del Prete says:
August 30, 2013 at 1:02 pm
I subscribe to Cliver and the like and not to your opinions Leif .
Cliver is a co-author of most of my papers on that subject and agrees with me. You cite an old and obsolete paper [you see, progress does happen]. And there is now general agreement that the aa index is seriously too low before 1957. You might also consult Figure 10 of http://www.leif.org/research/2009JA015069.pdf
Geomagnetic activity and the solar wind during the Maunder Minimum
Auteur(s) / Author(s)
CLIVER E. W. (1) ; BORIAKOFF V. (1) ; BOUNAR K. H. (2) ;
Affiliation(s) du ou des auteurs / Author(s) Affiliation(s)
(1) Air Force Research Laboratory, Hanscom Air Force Base, Massachusetts, ETATS-UNIS
(2) Radex, Inc., Bedford, Massachusetts, ETATS-UNIS
Résumé / Abstract
We used a strong (r = 0.96) correlation between 11-year averages of sunspot number (SSN) and the geomagnetic aa index to infer that the mean level of geomagnetic activity during the Maunder Minimum (1645-1715) was approximately a third of that observed for recent solar cycles (∼7 nT vs. ∼24 nT). We determined the variation of 11-year averages of solar wind speed (v) and the southward component of the interplanetary magnetic field (Bs) with cycle-averaged SSN for the two most recent cycles and also compared cycle-averaged variations of v2Bs and aa for the same interval. We then extrapolated these observed solar wind variations to Maunder Minimum conditions (mean SSN of ∼ 2 and mean aa value of ∼ 7 nT) to deduce that, on average, the solar wind during that period was somewhat slower (v = 340 ± 50 km s-1), and the interplanetary magnetic field much smoother (Bs = 0.3±0.1 nT), than at present (∼ 440 km s-1 and ∼ 1.2 nT). Various lines of evidence (including 10Be data) suggest that, despite the virtual absence of sunspots that characterized the Maunder Minimum, the 11-year geomagnetic (solar wind) cycle persisted throughout this period.
Revue / Journal Title
Geophysical research lettersISSN0094-8276CODEN GPRLAJ
Source / Source
Salvatore Del Prete says:
August 30, 2013 at 1:15 pm
Geomagnetic activity and the solar wind during the Maunder Minimum
CLIVER E. W. (1) ; BORIAKOFF V. (1) ; BOUNAR K. H. (2) ;
Ed Cliver now recognizes that he was wrong on that. Time that you accept his verdict.
There are two sides to this argument, just like the causes for prolonged solar minimum periods and what causes the climate to change which is not co2 ,butprolonged solar changes as shown in this article.
Past history supports all of this,and so will future history..
Leif whatever you say.
Among the little gems that I got out of this thread; other than the multi-layered rotation cells, was Leif’s statement, that only about 1 in 10,000 hydrogen atoms in the sun (surface ?) is ionized.
I had always pictured that there was just a sea of protons, in a cloud of electrons; (not because of any knowledge to that effect).
So it is nice to know that in our neighborhood plasma gizmo; hot as it is, it is still mostly neutral atoms. Leif sprinkles these things around, and you have to catch them, at the time, or lose out.
No Wiki, is not likely to save you from ignorance.
Encyclopediae seldom tell you anything useful. Oh they are exciting to read, about all kinds of stuff you never knew (or needed), or had the remotest interest in.
But turn to something you want to know, and it is never there; no matter what it is you look up.
It’s called “The Encyclopaedia Syndrome”, and it also infects, all on line help menus or telephone answering machine menus. No matter your problem, that you call for help on, it isn’t one of the things mentioned in the FAQs, and never context related to what you were doing when you got stalled.
I always keep pressing zero, until a human answers, or the phone hangs up.
Salvatore Del Prete says:
August 30, 2013 at 1:22 pm
Leif whatever you say.
Take that to heart and remember it well.
Geomagnetic activity and the solar wind during the Maunder Minimum
onlinelibrary.wiley.com › … › Vol 25 Issue 6 › Abstract
by EW Cliver – 1998 – Cited by 50 – Related articles
Dec 7, 2012 – Geomagnetic activity and the solar wind during the Maunder Minimum. Edward W. Cliver1,; Valentín Boriakoff1,; Khaled H. Bounar2 …. 14C record, Secular Solar and Geomagnetic Variations in the Last 10,000 Years, F. R. …
The 22-year cycle of geomagnetic and solar wind activity – Cliver …
onlinelibrary.wiley.com › … › Vol 101 Issue A12 › Abstract
by EW Cliver – 1996 – Cited by 88 – Related articles
Sep 20, 2012 – Edward W. Cliver; Valentín Boriakoff; Khaled H. Bounar … The amplitudes of the 22-year sunspot and geomagnetic activity
sep 2012 same
george e. smith says:
August 30, 2013 at 1:22 pm
Among the little gems that I got out of this thread; other than the multi-layered rotation cells, was Leif’s statement, that only about 1 in 10,000 hydrogen atoms in the sun (surface, yes) is ionized.
Another little gem: the density of the photosphere is only 1/1000 of the air at the surface of the Earth. And the pressure of the corona down on the surface is like that under one foot of a spider. And the energy generation by the fusion at the center is very gentle, like that of a compost heap [no exploding H-bombs]. Lots of those gems around…
Ap Index, Neutrons and Climate | Watts Up With That?
wattsupwiththat.com/2012/01/21/ap-index-neutrons-and-climate/
Jan 21, 2012 – The Ap Index is the weakest of the solar activity indicators and has …. I’v e checked the Hadcrut record and there was no cooling during this …
From richardscourtney on August 30, 2013 at 1:14 pm:
To clarify, as the speculation is getting ridiculous, I was a science credit short of a BS so it “defaulted” to a BA. That’s it.
Looks like this site is entertaining the theory .
Live and learn.