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Thread: Solar cycle #24

  1. #511
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    Does this mean Cycle 25 will be on Hold? Is it appropriate to speculate on local effects of such in this thread?

  2. #512
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    From what I've read in other articles, yes it could be delayed a few years.

  3. #513
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    Quote Originally Posted by Superluminal View Post
    From what I've read in other articles, yes it could be delayed a few years.
    What other articles are you referring to Superluminal?

    Three separate measured solar parameters have changed as noted in three separated published papers. The authors of the papers in question specifically state the observations in question indicate there has been a step change in the sun.

    http://www.bautforum.com/showthread....38#post1901338

    It has been known for sometime that the solar magnetic cycle varies cyclically with a period of 80 years, 200 years, 1470 years, and 2400 years.

    This is an exciting time as we will have a chance to watch a solar step change. From a solar physics standpoint a step change may provide the additional data required to solve some of the solar mysteries.

  4. #514
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    Interesting news from SDO about a technique for the early detection of sunspots

    http://sdoisgo.blogspot.com/2011/08/...-sunspots.html

    The paper referred to in the blog entry is here (journal subscription required)
    http://www.sciencemag.org/content/33...993.full?rss=1

    It will be interesting to see how such a technique might tune the observations used by thelivingstone & penn paper.

  5. #515
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    This the abstract from the paper.

    Sunspots are regions where strong magnetic fields emerge from the solar interior and where major eruptive events occur. These energetic events can cause power outages, interrupt telecommunication and navigation services, and pose hazards to astronauts. We detected subsurface signatures of emerging sunspot regions before they appeared on the solar disc. Strong acoustic travel-time anomalies of an order of 12 to 16 seconds were detected as deep as 65,000 kilometers. These anomalies were associated with magnetic structures that emerged with an average speed of 0.3 to 0.6 kilometer per second and caused high peaks in the photospheric magnetic flux rate 1 to 2 days after the detection of the anomalies. Thus, synoptic imaging of subsurface magnetic activity may allow anticipation of large sunspot regions before they become visible, improving space weather forecast.

  6. #516
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    Forgive me if that sounds a bit hyped to me! AFAIK, solar mass ejections and big flares don't necessarily happen just as the sunspots emerge, but take a little time to build up. I don't know exactly, but I'd guess an active region is usually around for something like a week, very roughly, before you get big storms, so knowing that a day in advance is a relatively small forecast advantage. What's more, when the Sun is active, you are probably a lot more worried about trying to figure out what is going to happen in the active regions that are already there, than you are going to worry about the ones that will appear tomorrow or the next day. But maybe at times when the Sun is not active, if you can see a big feature that is about to appear and give a surprise flare, it might be nice to know a day or two sooner. It's not insignificant, but a distasteful aspect of the whole field of "space weather" is the pervasive tendency to hype the basic science. To me, the advance here is simply in being able to better understand how sunspots emerge, by seeing them deeper.

  7. #517
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    Quote Originally Posted by Ken G View Post
    Forgive me if that sounds a bit hyped to me! AFAIK, solar mass ejections and big flares don't necessarily happen just as the sunspots emerge, but take a little time to build up. I don't know exactly, but I'd guess an active region is usually around for something like a week, very roughly, before you get big storms, so knowing that a day in advance is a relatively small forecast advantage. What's more, when the Sun is active, you are probably a lot more worried about trying to figure out what is going to happen in the active regions that are already there, than you are going to worry about the ones that will appear tomorrow or the next day. But maybe at times when the Sun is not active, if you can see a big feature that is about to appear and give a surprise flare, it might be nice to know a day or two sooner. It's not insignificant, but a distasteful aspect of the whole field of "space weather" is the pervasive tendency to hype the basic science. To me, the advance here is simply in being able to better understand how sunspots emerge, by seeing them deeper.
    I concur with your comment that observing the magnetic ropes that form sunspots deep within the sun cannot be used to predict solar flares. Every sunspot does not create a solar flare.

    What is interesting is the depth of the observations 65,000 km or 5 1/2 times the diameter of the earth. As I noted it is currently believed that sunspots are formed by magnetic ropes that are created at the tachocline (the name the narrow interface of the radiative zone and convection zone).

    This observation confirms the magnetic ropes rise up from a great depth in the sun.

    As noted in this thread Livingston and Penn have found the magnetic field strength of newly formed sunspots is decaying linearly. If the decay is extrapolated the sun will no longer be capable of forming sunspots by the year 2015. Something must happened deep within the sun to disturb the magnetic rope forming mechanism.

  8. #518
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    Quote Originally Posted by William View Post
    As noted in this thread Livingston and Penn have found the magnetic field strength of newly formed sunspots is decaying linearly. If the decay is extrapolated the sun will no longer be capable of forming sunspots by the year 2015. Something must happened deep within the sun to disturb the magnetic rope forming mechanism.
    The one problem with the Livingston and Penn paper is that they did not take all the sunspots into account. The smaller sunspots during the last sunspot cycle were not included in their sample. These smaller sunspots have weaker magnetic fields and, being left out of the paper, led to higher reported average of the field strength. If those spots were included, having a smaller field strength, the average of the last cycle may not be as high and the indicated decay of field strength may not be nearly as bad. Why Livingston and Penn did not include those spots is puzzling.

  9. #519
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    Quote Originally Posted by Tensor View Post
    The one problem with the Livingston and Penn paper is that they did not take all the sunspots into account. The smaller sunspots during the last sunspot cycle were not included in their sample. These smaller sunspots have weaker magnetic fields and, being left out of the paper, led to higher reported average of the field strength. If those spots were included, having a smaller field strength, the average of the last cycle may not be as high and the indicated decay of field strength may not be nearly as bad. Why Livingston and Penn did not include those spots is puzzling.
    Tensor,

    The magnetic rope that rises up through the convection zone to form sunspots on the surface of the sun requires a minimum magnetic strength (around 1500 gauss) to avoid being torn apart as it rises slow up through the turbulent convection zone.

    Livingston and Penn's analysis is indifferent to the total aggregate magnetic field of all the sunspots but rather is concerned with average maximum magnetic field strength of newly formed sunspots.

  10. #520
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    For those who may of missed this important announcement there are three separate solar observations that indicate the sun is heading towards a Dalton or Maunder minimum.

    Specifically what will happen next is not known.

    http://www.space.com/11960-fading-su...lar-cycle.html

    The results of the new studies were announced today (June 14) at the annual meeting of the solar physics division of the American Astronomical Society, which is being held this week at New Mexico State University in Las Cruces.

    "This is highly unusual and unexpected," said Frank Hill, associate director of the National Solar Observatory's Solar Synoptic Network. "But the fact that three completely different views of the sun point in the same direction is a powerful indicator that the sunspot cycle may be going into hibernation." ....
    Hill is the lead author of one of the studies that used data from the Global Oscillation Network Group to look at characteristics of the solar interior. (The group includes six observing stations around the world.) The astronomers examined an east-west zonal wind flow inside the sun, called torsional oscillation. The latitude of this jet stream matches the new sunspot formation in each cycle, and models successfully predicted the late onset of the current Cycle 24.

    "We expected to see the start of the zonal flow for Cycle 25 by now, but we see no sign of it," Hill said. "This indicates that the start of Cycle 25 may be delayed to 2021 or 2022, or may not happen at all."
    With more than 13 years of sunspot data collected at the McMath-Pierce Telescope at Kitt Peak in Arizona, Matt Penn and William Livingston observed that the average magnetic field strength declined significantly during Cycle 23 and now into Cycle 24. Consequently, sunspot temperatures have risen, they observed.

    If the trend continues, the sun's magnetic field strength will drop below a certain threshold and sunspots will largely disappear; the field no longer will be strong enough to overcome such convective forces on the solar surface.
    In a separate study, Richard Altrock, manager of the Air Force's coronal research program at NSO's facility in New Mexico, examined the sun's corona and observed a slowdown of the magnetic activity's usual "rush to the poles."

    "Cycle 24 started out late and slow and may not be strong enough to create a rush to the poles, indicating we'll see a very weak solar maximum in 2013, if at all," Altrock said. "If the rush to the poles fails to complete, this creates a tremendous dilemma for the theorists, as it would mean that Cycle 23's magnetic field will not completely disappear from the polar regions. … No one knows what the sun will do in that case."

  11. #521
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    Quote Originally Posted by William View Post
    Tensor,

    The magnetic rope that rises up through the convection zone to form sunspots on the surface of the sun requires a minimum magnetic strength (around 1500 gauss) to avoid being torn apart as it rises slow up through the turbulent convection zone.

    Livingston and Penn's analysis is indifferent to the total aggregate magnetic field of all the sunspots but rather is concerned with average maximum magnetic field strength of newly formed sunspots.
    Which still doesn't explain why they didn't include the smaller spots of the last cycle. Those spots reached the surface, so their strength had to be at least 1500 gauss, right? When they reached the surface, they were newly formed, right? The only major difference would be their field strength was not as great as the larger spots, but at least 1500 gauss. Which would have lowered the average. Not including them left the average higher.
    Last edited by Tensor; 2011-Aug-21 at 03:42 PM. Reason: Missed the last sentence

  12. #522
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    Tensor,

    I believe this quote explains why pores are not included in the direct analysis.

    http://iopscience.iop.org/1538-4357/..._649_1_L45.pdf

    Since measurements of pores may be contaminated with scattered light, we removed pores from this study. Pores in the data set can be identified from the daily drawings. The magnetic field strengths in pores range from 1600 to 2600 G with a mean of 2100 G.
    All data were acquired by Livingston with the National Solar Observatory 1.5 m McMath-Pierce (McM/P) telescope on Kitt Peak and its 13.5 m spectrometer. A 1 mm (2 .5#2 .5) Bowentype image slicer serves as an entrance slit of 0.1 mm width. After the 0.20 mm exit slit of the spectrograph, a single InSb diode measures the intensity spectrum as the grating is scanned over an interval of about 1.2 nm (for more details see Livingston 1991). System noise is negligible (the spectral signal-to noise ratio is 1103), although seeing and image position are always a concern. An umbral observation consists of five averaged scans with each umbra observed only once on a given day. Each day’s observation is treated independently of adjacent days; in general, we make no attempt to identify whether or not a given sunspot is recorded on multiple days.

    Necessary conditions for observing are a clear sky and fair to good seeing. With the image under guider control, the umbra is searched for the darkest position by visually checking a brightness meter. One seeks out what has been called a void.
    This is the darkest place that shows the least intensity structure. The spectral scans are made at this position, and then the image is moved to the nearby quiet photosphere (same limb distance) for a comparison intensity scan. A white-light full-disk sunspot drawing is also made on the McM/P 0.9 m west auxiliary telescope. As the observations are taken the spot positions are marked on this sketch. This is used to identify the sunspot type (spot or pore) and the limb distance.

  13. #523
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    Quote Originally Posted by William View Post
    Tensor,

    I believe this quote explains why pores are not included in the direct analysis.

    http://iopscience.iop.org/1538-4357/..._649_1_L45.pdf
    Don't think so. If it's such a problem, then why were they able to find the field strength in the pores? Or,why not use the infrared magnetic measurements, since those reduce scattered light to levels where the magnetic strength can be measured? And, correct me if I'm wrong, if they are not including the smaller sunspots, if it's known that the field strength of those sunspots are lower (how much lower doesn't matter), then isn't the average lower than they are reporting? And it's not me questioning this, I got my questions from several different solar scientists, when this was reported, so explain it to them.

  14. #524
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    The following links is broken?

  15. #525
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    They've reported a method of using helioseismology to make inferences about the onset of sunspot formation below the photosphere. Sunspots are essentially large concentrations of magnetic flux or flux ropes generated in the convective and seeded at the tachocline.

    It appears from the report that it gives an additional 2 days if a larger disturbance is detected.
    Detection depths for this method go down to 65Mm (the tachochline is 490Mm below the photosphere).

    They were not very clear about the the computed time-travel maps generated from the MDI data. Judging from the references this is a standard technique? I guess that from figure 1 in their paper that what they are doing is working out the shape of the wavefronts.

    The following slides are helpful in describing the technique
    http://soi.stanford.edu/~couvidat/STANFORD07.pdf

    As william suggests smaller sunspots don't always make it to the photosphere, how sensitive is the method and to what extent can it be used to detect thos sunspots which go missing?
    Last edited by mikeg64; 2011-Aug-23 at 02:51 PM. Reason: had some more questions/comments, reference

  16. #526
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    Quote Originally Posted by Tensor View Post
    Don't think so. If it's such a problem, then why were they able to find the field strength in the pores? Or,why not use the infrared magnetic measurements, since those reduce scattered light to levels where the magnetic strength can be measured? And, correct me if I'm wrong, if they are not including the smaller sunspots, if it's known that the field strength of those sunspots are lower (how much lower doesn't matter), then isn't the average lower than they are reporting? And it's not me questioning this, I got my questions from several different solar scientists, when this was reported, so explain it to them.
    Livingston and Penn note if the magnetic field strength of individual sunspots continues to decline the sun will no longer be capable of producing sunspots as the magnetic ropes that rise up from tachocline require a minimum field strength to resist being torn apart as they rise up through the turbulent convection zone.

    We will in next few years have an opportunity to determine if Livingston and Penn's analytical technique and prediction is valid.

    An interesting question to ask is how does the solar magnetic cycle restart when it has been interrupted. The current theory assumes that pieces of magnetic flux from the past cycle forms the seeds of the formation of the next cycles magnetic rope. If there are no sunspots what is the seed for the next cycle's sunspots?

  17. #527
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    Quote Originally Posted by William View Post
    Livingston and Penn note if the magnetic field strength of individual sunspots continues to decline the sun will no longer be capable of producing sunspots as the magnetic ropes that rise up from tachocline require a minimum field strength to resist being torn apart as they rise up through the turbulent convection zone.
    Which has what, exactly, to do with them ignoring the field strength of pores? What does this have to do with why Livingston and Penn giving a higher average field strength, when they know that pores have a lower field strength, but don't include them in the calculation of the values? It has nothing to do with either of the questions I posed.

    Quote Originally Posted by William View Post
    We will in next few years have an opportunity to determine if Livingston and Penn's analytical technique and prediction is valid.
    Based on what values? The ones with or without the pores included?

  18. #528
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    Quote Originally Posted by Tensor View Post
    Which has what, exactly, to do with them ignoring the field strength of pores? What does this have to do with why Livingston and Penn giving a higher average field strength, when they know that pores have a lower field strength, but don't include them in the calculation of the values? It has nothing to do with either of the questions I posed.


    Based on what values? The ones with or without the pores included?
    http://www.bautforum.com/showthread....22#post1926722

    I see what the problem is. The Science blog link summary article above incorrectly stated that Livingston and Penn are summing the magnetic field measurements of individual sunspots to determine the average magnetic field strength of the sun. That is not correct.

    Livingston and Penn are analyzing and concerned with the magnetic field strength of individual sunspots. Livingston and Penn have found that the magnetic field strength of each individual newly formed sunspot is declining linearly year by year. If one extrapolates the decline the magnetic field strength of the ropes that form the new sunspots will no longer be strong enough to survive the trip through the turbulent convection zone. The magnetic ropes will be torn apart.

    The magnetic field residue from sunspots forms the solar large scale magnetic field and is also the seeds for the next cycle's sunspots. If the sunspots absolutely disappear the regular mechanism (the seeds for the next year's cycle is the sunspots residue that moves up to the solar poles and then is moved down by convection into the solar tachocline) to generate sunspots will not function.

    Specifically what will happen next is not known from the standpoint of the sun. There are in the paleoclimatic record unexplained abrupt climate changes that coincide with cosmogenic isotope changes. There is a very regular paleoclimatic change that occurs with a frequency of 1470 years that Gerald Bond determined occurs at the same time as cosmogenic isotope changes which are caused by the sun (I believe he was able to track about 30 of the 1470 year cycles in the proxy records). In addition to the 1470 year cycle there are even larger climate change events with a frequency of roughly 8000 to 10,000 years that also have cosmogenic isotopes changes concern with the climate change event.

    This thread is currently in a holding pattern. The solar specialists have multiple theories to explain what is happening to the sun and there is no agreement as to which theory is correct and there is no one theory that explains all observations. I am looking for new observational data and/or papers related to this issue.

    Comment: I believe the solar pores are small pieces of the magnetic ropes that have been torn apart. The pores have a short lifetime on the surface of the sun. The number of pores is increasing.

  19. #529
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    Quote Originally Posted by William View Post
    http://www.bautforum.com/showthread....22#post1926722

    I see what the problem is. The Science blog link summary article above incorrectly stated that Livingston and Penn are summing the magnetic field measurements of individual sunspots to determine the average magnetic field strength of the sun. That is not correct.
    Of which I'm well aware. I read the paper, not the blog article. Remember, we were talking about the paper in posts 522 and 523.

    Quote Originally Posted by William View Post
    Livingston and Penn are analyzing and concerned with the magnetic field strength of individual sunspots. Livingston and Penn have found that the magnetic field strength of each individual newly formed sunspot is declining linearly year by year.
    Which still doesn't explain why they ignore the field strength of newly formed pores, last cycle. The sunspot field strength was stronger than the field strength for the pores. If the pores were included, the field strength would be lower. Which means, the rate of decrease would be lower. I've repeatedly asked the same question of you and you've now given me three different answers and one complete post that had nothing to do with the question, other than reasserting what Livingston and Penn said.

    First, in post #519 you said they ignored them because their field strength was large enough to avoid being torn apart.

    Second, I pointed out that if a pore is on the surface, it's field strength has to be at least at the minimum. You pointed me to their paper, in Post #522, using a quote indicating they couldn't measure the field strength of the pores.

    Third, I pointed out that the paper indicates that magnetic field strength was found for pores. In Post #526, you didn't even pretend to answer the question. Just reasserted the claim.

    Fourth, I asked what your answer had to do with Livingston and Penn ignoring the pore's magnetic field strength. You give us Post #528, telling me the blog post was giving out wrong data. Seemingly forgetting that we've already talked about the paper itself, not the blog post. And then, simply repeating the assertation that the Livingston and Penn found the field strength declining linearly. Yes, we know that what they found, you mention it every post. The question is, are their conclusions valid if they ignore smaller pore's magnetic field strength, which would change the rate at which the field strength would be declining?

    If you don't have an answer, just say so. But their non-inclusion of the pores is a valid criticism of the value found for the field strength in the last cycle.

  20. #530
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    As noted in this review article the magnetic ropes that rise up through the convection zone to form sunspots on the surface of the sun are believed to be formed in the tachocline the name for a thin stable region that separates the turbulent solar convection zone from the solar radiative zone.

    The seeds for the next solar cycle are the remnants of sunspots from the last solar cycle which travel down by convection to the tachocline. At the tachocline the magnetic remnants are amplified. When they reach a certain strength they are released.

    http://solarphysics.livingreviews.or...009-4Color.pdf

    Magnetic Fields in the Solar Convection Zone

    Active regions on the solar surface are generally thought to originate from a strong toroidal magnetic field generated by a deep seated solar dynamo mechanism operating at the base of the solar convection zone. Thus the magnetic fields need to traverse the entire convection zone before they reach the photosphere to form the observed solar active regions. Understanding this process of active region flux emergence is therefore a crucial component for the study of the solar cycle dynamo. This article reviews studies with regard to the formation and rise of active region scale magnetic flux tubes in the solar convection zone and their emergence into the solar atmosphere as active regions.
    The cyclic large scale magnetic field of the Sun with a period of 22 years is believed to be sustained by a dynamo mechanism (see e.g. review by Charbonneau, 2005). The Hale polarity law of solar active regions indicates the presence of a large scale subsurface toroidal magnetic field generated by the solar cycle dynamo mechanism.
    The picture of how and where the large scale solar dynamo operates has undergone substantial revision due in part to new knowledge from helioseismology regarding the solar internal rotation profile (see Deluca and Gilman, 1991; Gilman, 2000). Evidence now points to the tachocline, the thin shear layer at the base of the solar convection zone, where solar rotation changes from the latitudinal differential rotation of the solar convective envelope to the nearly solid-body rotation of the radiative interior, as the site for the generation and amplification of the large scale toroidal magnetic field from a weak poloidal magnetic field (see Charbonneau and MacGregor, 1997; Dikpati and Charbonneau, 1999; Dikpati and Gilman, 2001). Furthermore, with its stable (weakly) subadiabatic stratification, the thin overshoot region in the upper part of the tachocline layer (Gilman, 2000) allows storage of strong toroidal magnetic fields against their magnetic buoyancy for time scales comparable to the solar cycle period (Parker, 1975, 1979; van Ballegooijen, 1982; Moreno-Insertis et al., 1992; Fan and Fisher, 1996; Moreno-Insertis et al., 2002; Rempel, 2003). Thus with toroidal magnetic fields being generated and stored in the tachocline layer at the base of the solar convection zone, these fields need to traverse the entire convection zone before they can emerge at the photosphere to form the observed solar active regions.

    Observations and modeling analysis to support the statement in the above review article. (I also found a review paper written by Eugene Parker the originator of the superseded theory that sunspots are formed in the convection zone acknowledging that observational evidence does not support that mechanism.)

    http://www.sciencemag.org/content/29.../1671.abstract
    Explaining the Latitudinal Distribution of Sunspots with Deep Meridional Flow
    Sunspots, dark magnetic regions occurring at low latitudes on the Sun's surface, are tracers of the magnetic field generated by the dynamo mechanism. Recent solar dynamo models, which use the helioseismically determined solar rotation, indicate that sunspots should form at high latitudes, contrary to observations. We present a dynamo model with the correct latitudinal distribution of sunspots and demonstrate that this requires a meridional flow of material that penetrates deeper than hitherto believed, into the stable layers below the convection zone. Such a deep material flow may have important implications for turbulent convection and elemental abundance in the Sun and similar stars.
    http://astronomy.ege.edu.tr/~rpekunlu/MHDII/Dikpati.pdf

    STABILITY ANALYSIS OF TACHOCLINE LATITUDINAL DIFFERENTIAL ROTATION AND COEXISTING TOROIDAL BAND USING A SHALLOW-WATER MODEL
    Recently global, quasi-two-dimensional instabilities of tachocline latitudinal differential rotation have been studied using a so-called shallow-water model. While purely hydrodynamic shallow-water type disturbances were found to destabilize only the overshoot tachocline, the MHD analysis showed that in the presence of a broad toroidal field, both the radiative and overshoot parts of the tachocline can be unstable. We explore here instability in the shallow-water solar tachocline with concentrated toroidal bands placed at a wide range of latitudes, emulating different phases of the solar cycle. In equilibrium, the poleward magnetic curvature stress of the band is balanced either by an equatorward hydrostatic pressure gradient or by the Coriolis force from a prograde jet inside the band. We find that toroidal bands placed almost at all latitudes make the system unstable to shallow-water disturbances. For bands without prograde jets, the instability persists well above 100 kG peak field, while a jet stabilizes the band at a field of _40 kG.

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    http://books.google.ca/books?id=Yh3b...Parker&f=false

    http://www.google.ca/url?sa=t&source...mnb8UA&cad=rja

    Solar Magnetism: The State of Our Knowledge and Ignorance
    Eugene Parker

    Leighton (1969) remarked many years ago that “were it not for the magnetic fields, the Sun would be as uninteresting as most astronomers seem to think it is”; this is the stuff that makes science so fascinating. So it is the purpose of this writing to review some of our outstanding ignorance of the physics of solar magnetism and to give an example of a fresh approach to the solar dynamo.

    Consider, then a minimum estimate of the azimuthal magnetic field strengths to encountered in the convection zone of the Sun. It is general believed that the azimuthal magnetic field of the Sun is created in the tachocline – the layer of intense shear at the bottom of the convection zone. The magnetic field is buoyant and subject to upward eruption, form the alpha-loops that emerge at the visible surface to form the active bipolar magnetic regions. ….

    …It is evident the convection may distort the mean field in substantial ways, but the turbulent mixing process is largely stymied, and it appear the concept of turbulent diffusion of magnetic fields cannot be applied to the azimuthal magnetic field in the convection zone of the Sun. There is no way to account for the value n approx. 10^12 cm^2/sec, suggesting it is necessary to rethink the alpha omega dynamo for the sun.
    Last edited by William; 2011-Sep-10 at 02:41 AM.

  22. #532
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    Quote Originally Posted by William View Post
    Observations and modeling analysis to support the statement in the above review article. (I also found a review paper written by Eugene Parker the originator of the superseded theory that sunspots are formed in the convection zone acknowledging that observational evidence does not support that mechanism.)
    But NOBODY ever claimed that sunspots are formed in the convection zone, that is your apparent misreading of various posts by various posters.
    It was stated that magnetic fields are generated in the convection zone through the alpha-omega dynamo. Now it seems that the region near the tachocline is also important for the azimuthal fields and models will be adjusted.
    However, this has NOTHING to do with sunspots, as it is still emerging magnetic flux tubes through the photosphere (surface of the Sun) which creates the sunspots, even in e.g. Zirker's book "the magnetic universe." (chapter 2 gives a very nice summary of the solar magnetic field and its generation)
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  23. #533
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    Quote Originally Posted by tusenfem View Post
    But NOBODY ever claimed that sunspots are formed in the convection zone, that is your apparent misreading of various posts by various posters.
    It was stated that magnetic fields are generated in the convection zone through the alpha-omega dynamo. Now it seems that the region near the tachocline is also important for the azimuthal fields and models will be adjusted.

    However, this has NOTHING to do with sunspots, as it is still emerging magnetic flux tubes through the photosphere (surface of the Sun) which creates the sunspots, even in e.g. Zirker's book "the magnetic universe." (chapter 2 gives a very nice summary of the solar magnetic field and its generation)
    I did not state sunspots are formed in the tachocline. I stated that the fundamental magnetic ropes that will organize on the surface of the sun to become sunspots are formed in the tachocline. The magnetic ropes are released at the tachocline and they then rise up to surface of the sun and were they merge and organize to become the sunspots.

    The sunspot have a complex structure which includes flux tubes. The creation of the basic very strong magnetic fields occurs at the tachocline.

    There is a NASA satellite movie of the formation of a sunspot. The process of organization of the very strong magnetic fields of the ropes to become a sunspot looks like some kind of prehistoric creature that thrashes and wiggles until the fields reach a dynamically stable configuration.

    From Jack Zirker‘s book which I would highly recommend Journey from the Center of the Sun.

    In the midst of all the post-mortems, the first helioseismic maps of solar rotation were published. As we saw in chapter 5, these maps showed that at each solar latitude, the top and bottom of the convection zone have about the same rotation speed, contrary to the assumptions of kinematic and dynamic modelers!

    Other problems with solar cycle models began to surface. They centered on those magical magnetic ropes that turned into sunspots. As we know, the field strength in a large spot can reach 3000 gauss. In order for the field to build up to this level the sun would need sufficient time to wrap a weak polar field many times around the equator. But Gene Parker showed in 1975 that a buoyant rope would rise through the convection zone in much less than eleven years and would reach the with fields much weaker than 3000 gauss. How could the rope remain submerged long enough?

    Even worse, a rope with a field strength of only 3000 gauss would be chewed to bits by the vigorous convection cells it passes on its way to the surface. A field strength of a least 10,000 gauss and possibly 30,000 gauss would need to survive the trip.
    That raises another problem. Such strong fields would be stiff. They would resist being twisted by cyclonic convection. The alpha effect would be suppressed and the dynamo would stutter to a halt.

    Several theorists ...that the ideal place to store a magnetic rope was just beneath the convection zone, at the boundary with the radiative zone. ...
    Another nice feature of this overshoot regions is its shear.
    Last edited by William; 2011-Sep-11 at 03:05 PM.

  24. #534
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    The following is a movie that shows the heliosiesmic mapping of strong magnetic ropes as they rise up through the convection zone. A subsequent multi spectral movie shows the magnetic ropes as they organize themselves on the surface of the sun to form a sunspot.

    As Eugene Parker and others noted, the magnetic ropes require a magnetic field strength of 10,000 to 30,000 gauss to avoid being torn apart by the strong strong convection currents in the solar convection zone. The magnetic ropes can therefore not form in the convection zone. (i.e. The magnetic ropes require a very strong field strength to resist being torn apart. They must be formed in a region where they are protected from the strong convection currents to allow them to build up the necessary field strength to survive the floating trip up from the tachocline to solar surface.)

    The magnetic ropes are hypothesized to form in the tachocline which is a narrow stable region in the sun that separates the radiative zone from the convection zone.

    I have started to look at the mechanisms by which the magnetic ropes are hypothesized to be created at the tachocline. Perhaps solar cycle 24 observation data will help theorists solve this problem.

    http://soho.esac.esa.int/hotshots/2011_09_01/ar1158.mp4

    Movie shows the detected travel-time perturbations during the emergence of active region 11158. First 12 seconds of the movie show photospheric intensity observations (orange color) of the region, and travel-time perturbations detected at a depth of about 60,000 km (blue-red color). Then, movie shows sunspots (blue and orange) on the solar surface and coronal loops (light green) observed by SDO/AIA. (Movie made by T. Hartlep and S. Winegarden)
    http://soho.esac.esa.int/hotshots/index.html/

  25. #535
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    Quote Originally Posted by William View Post
    I did not state sunspots are formed in the tachocline. I stated that the fundamental magnetic ropes that will organize on the surface of the sun to become sunspots are formed in the tachocline. The magnetic ropes are released at the tachocline and they then rise up to surface of the sun and were they merge and organize to become the sunspots.

    The sunspot have a complex structure which includes flux tubes. The creation of the basic very strong magnetic fields occurs at the tachocline.

    There is a NASA satellite movie of the formation of a sunspot. The process of organization of the very strong magnetic fields of the ropes to become a sunspot looks like some kind of prehistoric creature that thrashes and wiggles until the fields reach a dynamically stable configuration.

    From Jack Zirker‘s book which I would highly recommend Journey from the Center of the Sun.
    And apparently you cannot read and don't understand what you read.
    It was not claimed that you stated that sunspots are formed at the tachocline.
    You did state however (and somehow including me in that too): Eugene Parker the originator of the superseded theory that sunspots are formed in the convection zone, which I greatly doubt that you can find that Parker claimed that.
    You are mixing up (A)the creation of magnetic flux tubes through the variouis dynamo processes taking place in the sun and (B) the emergence of these flux tubes creating the sunspots that we see on the surface of the Sun.

    And though Zirker writes nicely, there is little physics in his books. It would be better if you actually studied the other book (from which Parker's paper's references were quoted) Michael Thompson - The Origin and Dynamics of Solar Magnetism (Springer, 2009), where you will find a lot of very high quality paper on (amongst others) dynamo processes in the Sun to generate the magnetic fields.

    Some examples:
    Weiss and Thompson: The Solar Dynamo
    Quote Originally Posted by abstract
    It is generally accepted that the strong toroidal magnetic fields that emerge through the solar surface in sunspots and active regions are formed by the action of differential rotation on a poloidal field, and then stored in or near the tachocline at the base
    of the Sun’s convection zone. The problem is how to explain the generation of a reversed poloidal field from this toroidal flux—a process that can be parametrised in terms of an α-effect related to some form of turbulent helicity. Here we first outline the principal patterns that have to be explained: the 11-year activity cycle, the 22-year magnetic cycle and the longer term modulation of cyclic activity, associated with grand maxima and minima. Then we summarise what has been learnt from helioseismology about the Sun’s internal structure and rotation that may be relevant to our subject. The ingredients of mean-field dynamo models are differential rotation, meridional circulation, turbulent diffusion, flux pumping and the α-effect: in various combinations they can reproduce the principal features that are observed. To proceed further, it is necessary to rely on large-scale computation and we summarise the current state of play.
    or Dikpati & Gilman: Flux-Transport Solar Dynamos
    Quote Originally Posted by abstract
    Large-scale solar dynamo models were first built by Parker (1955). Over the past half a century these models have evolved significantly.We discuss here the development of a class of large-scale dynamo models which include, along with the α-effect and Ω-effect, an important third process, flux transport by meridional circulation. We present the properties of this ‘flux-transport’ dynamo, including the crucial role meridional circulation plays in giving this dynamo predictive power.
    Or Tobias: The Solar Dynamo: The Role of Penetration, Rotation and Shear on Convective Dynamos
    Quote Originally Posted by abstract
    In this paper I discuss the importance of turbulence, rotation, penetration and shear for solar dynamos (both local and global). An understanding of these processes is vital for progress towards a self-consistent theory for the generation of solar magnetic activity.
    I discuss the difficulties for large-scale field generation and suggest that large-scale solar magnetic activity may be driven by dynamos that arise owing to instabilities, with these dynamos modified by the presence of turbulence.
    or Kosovichev: Photospheric and Subphotospheric Dynamics of Emerging Magnetic Flux
    Quote Originally Posted by abstract
    Magnetic fields emerging from the Sun’s interior carry information about physical processes of magnetic field generation and transport in the convection zone. Soon after appearance on the solar surface the magnetic flux gets concentrated in sunspot regions and causes numerous active phenomena on the Sun. This paper discusses some properties of the emerging magnetic flux observed on the solar surface and in the interior. A statistical analysis of variations of the tilt angle of bipolar magnetic regions during the emergence shows that the systematic tilt with respect to the equator (the Joy’s law) is most likely established
    below the surface. However, no evidence of the dependence of the tilt angle on the amount of emerging magnetic flux, predicted by the rising magnetic flux rope theories, is found. Analysis of surface plasma flows in a large emerging active region reveals strong
    localized upflows and downflows at the initial phase of emergence but finds no evidence for large-scale flows indicating future appearance a large-scale magnetic structure. Local helioseismology provides important tools for mapping perturbations of the wave speed and mass flows below the surface. Initial results from SOHO/MDI and GONG reveal strong diverging flows during the flux emergence, and also localized converging flows around stable sunspots. The wave speed images obtained during the process of formation of a large active region, NOAA 10488, indicate that the magnetic flux gets concentrated in strong field structures
    just below the surface. Further studies of magnetic flux emergence require systematic helioseismic observations from the ground and space, and realistic MHD simulations of the subsurface dynamics.
    And also Parker's paper in that book should be taken as a discussion starting point for the whole book that follows afterward.

    So, please take care about what exactly you are talking, emergence of flux tubes through the surface of the Sun or the generation of these flux tubes in the layers below the photosphere.
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  26. #536
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    Quote Originally Posted by William View Post
    I have started to look at the mechanisms by which the magnetic ropes are hypothesized to be created at the tachocline. Perhaps solar cycle 24 observation data will help theorists solve this problem.

    Movie shows the detected travel-time perturbations during the emergence of active region 11158. First 12 seconds of the movie show photospheric intensity observations (orange color) of the region, and travel-time perturbations detected at a depth of about 60,000 km (blue-red color). Then, movie shows sunspots (blue and orange) on the solar surface and coronal loops (light green) observed by SDO/AIA. (Movie made by T. Hartlep and S. Winegarden)
    http://soho.esac.esa.int/hotshots/2011_09_01/ar1158.mp4
    I fail to see what observations at a depth of 60.000 km in the sun have to do with the tachocline, which is at about 210.000 km depth.
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  27. #537
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    Quote Originally Posted by tusenfem View Post
    I fail to see what observations at a depth of 60.000 km in the sun have to do with the tachocline, which is at about 210.000 km depth.
    tunenfem,

    I know what depth the tachocline is at. Why state that? The limit of detection of the magnetic ropes by heliosiesmic mapping is 60,000 km. These very strong magnetic ropes float up from a depth greater than 60,000 km to form sunspots.

    The magnetic ropes require a field strength of 10,000 gauss to 30,000 gauss to avoid being torn apart in the convection zone. Do you agree or disagree with that statement?

    Are you stating that extremely strong magnetic fields sink in the convection zone?

    Are we in agreement that the very strong magnetic ropes are formed in the tachocline?

    Did you see the sunspot heliosiesmic observations where the researchers specifically state that they were surprised at how shallow the sunspots are?

    Watch the video of the magnetic ropes rising up through the convection zone. The next video is a sunspot forming in the region where the magnetic ropes that were detected by heliosiesmic observations floated up to. What is your interpretation of what is happening?

  28. #538
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    tunenfem,

    I am stating that the powerful magnetic fields that rise up to form sunspots are formed in the tachocline. Do you agree or disagree with that statement?

    http://adsabs.harvard.edu/abs/2004cosp...35.1198D

    The importance of the solar tachocline
    The solar tachocline, a thin layer containing the strong radial differential rotation, at the base of the convection zone, has proven to be important for the following reasons: (i) radial shear there is likely to generate the Sun's strongest toroidal fields, which eventually erupt as bipolar spots at the surface; (ii) it provides a good location for magnetic flux-storage. The subadiabatic stratification of this layerallows storage of strong toroidal field despite its magnetic buoyancy, while toroidal bands are held against poleward slip by either the prolateness of this layer, or by jet-like flows within the band, or both; (iii) global HD and MHD instabilities that are theoretically predicted to occur in this layer produce two major results. One is the production of large-scale non-axisymmetries, by tipping or deforming the toroidal band, and the other is the generation of kinetic helicity. Both have important implications in solar dynamos. The former could be responsible for producing the Sun's "active-longitudes", while the latter produces the extended dipolar poloidal fields that are necessary for magnetically coupling the Sun's N- and S-hemispheres. We will review these theoretical results, and indicate features to look for in the helioseismic data, such as, prolateness, amplitude and location of jet in the tachocline, their variations with solar cycle and detection of helical flow and its spatial and temporal dependence

  29. #539
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    Quote Originally Posted by William View Post
    tunenfem,

    I know what depth the tachocline is at. Why state that? The limit of detection of the magnetic ropes by heliosiesmic mapping is 60,000 km. These very strong magnetic ropes float up from a depth greater than 60,000 km to form sunspots.

    The magnetic ropes require a field strength of 10,000 gauss to 30,000 gauss to avoid being torn apart in the convection zone. Do you agree or disagree with that statement?

    Are you stating that extremely strong magnetic fields sink in the convection zone?
    If you would read what I wrote you would not post these questions.

    Quote Originally Posted by William View Post
    Are we in agreement that the very strong magnetic ropes are formed in the tachocline?

    Did you see the sunspot heliosiesmic observations where the researchers specifically state that they were surprised at how shallow the sunspots are?

    Watch the video of the magnetic ropes rising up through the convection zone. The next video is a sunspot forming in the region where the magnetic ropes that were detected by heliosiesmic observations floated up to. What is your interpretation of what is happening?
    The tachocline seems to be important.

    For the rest you are just expanding the topic further and further, bringing in new stuff to obfuscate that you keep on making claims that are incorrect about what other posters have written.

    I am not interested in such a game.

    And by the way, learn to spell my name correctly, thank you very much.
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  30. #540
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    tusenfem,

    The problem is you just cannot admit your were incorrect. You specifically stated "So, the idea of magnetic field ropes being created at the tachocline and "fighting their way through the convection zone" is highly incorrect"

    Then you add a number of quotes that have nothing to do validating your incorrect statement. Then you state if I read your comment I would understand what you mean. The problem as I stated above is you cannot admit you were incorrect. I do not have that problem.

    If you have a specific scientific comment please explain it to me and others in the forum.

    The magnetic ropes are formed at the tachocline. They rise up to form sunspots on the surface of the sun.

    I agree that sunspots are not formed at the tachocline. The magnetic ropes that rise up to the surface of the sun form the sunspots.

    tusenfem said:

    http://www.bautforum.com/showthread....55#post1617955

    Originally Posted by William:Assuming the magnetic rope which forms sunspots is produced at the tachocline (interface of the solar radiative zone and the solar convection zones), if the magnetic rope field strength is weak the rope is twisted and pulled apart as it moves through the convection zone, which would explain why weak sunspots can be either normal or reversed magnetic polarity.

    Tusenfem said: I am sorry, but I have to disagree here. The tachocline is the boundary between the radiative zone and the convection zone deep inside the sun. Now, onlz in the convective region can magnetic field be generated and amplified by the so called α and ω dynamo processes can happen.

    It is not that immedately at this boundary magnetic field is generated and "has to travel through the ominous convective zone" and survive or not. In any plasma there will be small loops of magnetic field generarated through random processes. Only when there is some mechanism that can amplify these seed fields (a dynamo) can there be significant magnetic field in the end. The best and most comprehensive description of the α-ω dynamo in my view has been written by my good friend and colleague Karl-Heinz Glassmeier (in the introduction part, forget about the feedback mechanism). The passage of the seed fields through the convection zone will cause the magnetic field to be amplified.

    So, the idea of magnetic field ropes being created at the tachocline and "fighting their way through the convection zone" is highly incorrect.

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