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Post by Maui on Mar 9, 2011 19:48:42 GMT
"The unusual minimum of sunspot cycle 23 caused by meridional plasma flow variations," Dibyendu Nandy, Andrés Muñoz-Jaramillo, & Petrus C. H. Martens; Nature 471, 80–82, 03 March 2011
DOI:
doi:10.1038/nature09786
David Hathaway commented: "This theoretical model is diametrically opposed to the observations of Hathaway & Rightmire (2010) Science, 327, 1350."
I do not understand why the model generates a five-year solar cycle (Figure 1, simulated butterfly diagram). The first author responded to me by email, "One can yield a 11 year cycle exactly, by fine tuning the parameters, which we did not attempt to do. We do not learn anything about the physics of the solar cycle by this fine tuning." But all the other "parameters" are realistic. Is the author saying the model will produce ANY desired result merely "by fine tuning the parameters?"
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Post by Maui on Mar 10, 2011 2:58:56 GMT
...no response yet... even in this age of instant data, the exchange of information is hampered by time zones. I check email on my lunch break (PST/PDT), the corresponding author is in India, and it all has to be mediated by editors in England...
Dr. Nandy, is Figure 1 off by a factor of two or what? Who ever heard of five-year solar cycles? What are the units for polar field strength?
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Post by Bob k6tr on Mar 10, 2011 3:19:18 GMT
...no response yet... even in this age of instant data, the exchange of information is hampered by time zones. I check email on my lunch break (PST/PDT), the corresponding author is in India, and it all has to be mediated by editors in England... Dr. Nandy, is Figure 1 off by a factor of two or what? Who ever heard of five-year solar cycles? What are the units for polar field strength? Maui there are several questions I have about Nandi's theories but I have yet to get a complete picture about what he is saying. From what I have learned it appears that Nandi is taking Mausumi Dikpati's Ideas and standing them on their head. Which makes me wonder if this is genuine scientific research or is he just creating rationalizations. Nonetheless I still have yet to reach any conclusions about the work. |
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Post by Maui on Mar 10, 2011 18:26:50 GMT
It is my opinion that the meridional flow is not quite as simple as these models. This reminds me of a discussion of Earth's mantle convection I had with University of Hawai'i Prof. John Sinton. I asked how one could reconcile the Hawai'ian hot-spot with Don Anderson's (Cal Tech) computer model, which predicts downwelling mantle beneath the islands. Sinton responded, with a big smile and a wave of his hand:
"The models can make the mantle go up or they can make it go down."
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Post by vukcevic on Mar 10, 2011 19:58:59 GMT
..........there are several questions I have about Nandi's theories but I have yet to get a complete picture about what he is saying. ........ On Meridional flow ‘modelling’ only worth reading are Evolution of polar fields by Wang , Lean and Sheeley- from Hulburt Center for Space Research, Naval Research Lab, Washington and Evolution of the large-scale magnetic field by Solanki, Baumann, Schmitt & Schüssler – from Max Planck Institut . You can find links here: www.vukcevic.talktalk.net/LFC17.htm
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Post by Maui on Mar 10, 2011 22:01:40 GMT
..........there are several questions I have about Nandi's theories but I have yet to get a complete picture about what he is saying. ........ On Meridional flow ‘modelling’ only worth reading are Evolution of polar fields by Wang , Lean and Sheeley- from Hulburt Center for Space Research, Naval Research Lab, Washington and Evolution of the large-scale magnetic field by Solanki, Baumann, Schmitt & Schüssler – from Max Planck Institut . These are both cited in Nandy et al.Wang, Y.-M., Robbrecht, E. & Sheeley, N. R., Jr On the weakening of the polar magnetic fields during solar cycle 23. Astrophys. J. 707, 1372–1386 (2009) Solanki, S. K., Schüssler, M. & Fligge, M. Evolution of the Sun’s large-scale magnetic field since the Maunder minimum. Nature 408, 445–447 (2000) From Charbonneau, P. Dynamo models of the solar cycle. Living Rev. Solar Phys. 7, 3 solarphysics.livingreviews.org/Articles/lrsp-2010-3/ (2010) I close this review with the following discussion of a few open questions that, in my opinion, bear particularly heavily on our understanding (or lack thereof) of the solar cycle.
6.1 What is the primary poloidal field regeneration mechanism?
6.2 What limits the amplitude of the solar magnetic field?
6.3 Flux tubes versus diffuse fields
6.4 How constraining is the sunspot butterfly diagram?
6.5 Is meridional circulation crucial?
6.6 Is the mean solar magnetic field really axisymmetric?
6.7 What causes Maunder-type Grand Minima?
6.8 Where do we go from here? edited for punctuation |
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Post by Maui on Mar 12, 2011 21:58:41 GMT
I feel the authors have not given a satisfactory explanation of why their model is based on an 8.9-year solar cycle. This is their figure; I see at least one 5-year solar cycle in the sample of forty years, and with six cycles visible the period is 40 / 6 or 6.7 years).
But even an 80% (8.9-yr) sunspot cycle does not make sense. The authors say they can fine-tune the plasma flow rate parameters to achieve an 11-year cycle, but this is varying the precise parameter that they are evaluating as the cause. What about the other parameters? Number of days between cycles with no sunspots is an important element here, but how do they define "day?" Is it only 80% of 24 hours? How do they define "sunspot?"
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Post by Maui on Mar 14, 2011 15:42:14 GMT
My latest comment (paraphrased above) has been accepted by Nature and posted on their forum. I probably would not be so persistent if David Hathaway himself had not challenged their conclusions.
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Post by Maui on Mar 15, 2011 15:20:52 GMT
Ack! Nature is hacked this morning... "March 1, 2011: NPG is investigating network issues affecting access to www.nature.com. " |
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Post by Maui on Mar 16, 2011 15:13:09 GMT
Muñoz-Jaramillo responded that a referee had posed this question, and it is addressed in the Supplementary Information. Fortunately, I am a paid subscriber and have access to this; unfortunately, their web site is down again.
I remember looking over the supplementary information to find where it addressed Hathaway's even more significant challenge. It's all smoke and mirrors; Hathaway called it, "hand waving."
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Post by Maui on Mar 19, 2011 17:56:24 GMT
Ack!! Now I've been hacked!
My research "vacation" (a few "planned" days off work) will start as soon as I can find the right answer to my question. I have only found painful answers to the question, "How do you remove bandages after surgery?" This is not satisfactory.
If I do a search for answers to, "Will this power plant survive an earthquake?"--well, you can find whatever answers you want. The study of meridional flow on the Sun creates a question ("Can we model this?"), so of course they are able to create an answer.
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Post by Maui on Apr 4, 2011 18:06:11 GMT
A review of the model is "Story One" in Science News last week (Ron Cowen, "Spots suggest sun's doldrums likely to continue," March 26 2011, pp. 5-6). There is no mention of the unusual solar cycle duration.
An author has responded that a Referee raised this question, and apparently it was answered to the satisfaction of the Editors. Interestingly, there is this incorrect statement in the Editor's Summary: ""The Sun is currently extremely active..." (http://www.nature.com/nature/journal/v471/n7336/full/nature09786.html).
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