On the Origin of Solar and Stellar Magnetic Fields

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On the Origin of Solar and Stellar Magnetic Fields

There is recent evidence that the solar magnetic cycle has been interrupted.

This is a link to Livingston and Penn’s paper that notes the magnetic field strength of newly formed sunspots is decreasingly linearly. Specifically, why the magnetic field strength of newly formed sunspots is decreasing is not known. There is in the paleoclimatic record evidence of unexplained cyclic abrupt climate changes (Bond events and Heinrich events) that correlate with abrupt cosmogenic isotope changes. The cosmogenic isotope changes are known to be caused by solar magnetic cycle changes and by geomagnetic field changes. It is time for the next 1470 year Bond climate change event and the next 8,000 to 10,000 year Heinrich event (It appears the Heinrich event is a very, very, strong Bond event). Assuming the sun was the cause of the past Bond and Heinrich events, the solar magnetic cycle from time to time is interrupted. Based on an assume mechanism that explains what is observed in the paleo record, the restart of the solar magnetic cycle is what causes the Bond and Heinrich events.

I am not interesting in discussing the fundamental mechanisms (solar, geomagnetic, and atmospheric) how a solar magnetic cycle interruption could physically cause what is observed unless there is definitive evidence that the solar magnetic cycle has been interrupted in an anomalous manner as opposed to a normal cyclic slowdown of the solar magnetic cycle. There may be a number of months or years before there is evidence to resolve this question.

I will however start a separate thread to discuss structured astronomical anomalies which appear to point to a possible theoretical explanation. (i.e. I have been specifically looking for astronomical evidence to construct and support a strawman mechanism. What I found is interesting regardless of whether it does or does not support a new mechanism for the generation of astronomical magnetic fields.)


http://arxiv.org/abs/1009.0784

Long-term Evolution of Sunspot Magnetic Fields
Independent of the normal solar cycle, a decrease in the sunspot magnetic field strength has been observed using the Zeeman-split 1564.8nm Fe I spectral line at the NSO Kitt Peak McMath-Pierce telescope. Corresponding changes in sunspot brightness and the strength of molecular absorption lines were also seen. This trend was seen to continue in observations of the first sunspots of the new solar Cycle 24, and extrapolating a linear fit to this trend would lead to only half the number of spots in Cycle 24 compared to Cycle 23, and imply virtually no sunspots in Cycle 25...

We reported in Penn & Livingston (2006) that a time series of this magnetic field data showed a decrease in the umbral magnetic field strength which was independent of the normal sunspot cycle. Also, the measurements revealed a threshold magnetic field strength of about 1500 Gauss, below which no dark pores formed. A linear extrapolation of the magnetic field trend suggested that the mean field strength would reach this threshold 1500 Gauss value in the year 2017. Furthermore, analysis of the umbral continuum brightness showed another linear trend, and extrapolation showed the umbral brightness would be equal to the quiet Sun brightness at about the same year. Finally, the molecular line depths showed a decreasing strength with time, and again the trend suggested that molecular absorption lines would disappear from the average sunspot umbra near 2017.
There is a suite of recent astronomical and solar observational evidence that supports the assertion that the assumed fundamental mechanisms by which magnetic fields are created in stellar and very large astronomical bodies is incorrect. The seismological evidence that the solar convection is 20 to 100 times less than theoretically assumed which makes the assumed mechanism to generate the solar magnetic field not possible is only one of many.

“If these motions are indeed that slow in the Sun, then the most widely accepted theory concerning the generation of solar magnetic field is broken, leaving us with no compelling theory to explain its generation of magnetic fields and the need to overhaul our understanding of the physics of the Sun’s interior.”

http://www.nyu.edu/about/news-publi...-create-mri-of-the-suns-interior-motions.html

Anomalously Weak Solar Convection
Once the scientists captured the precise movement waves on the Sun’s surface, they were able to calculate its unseen plasma motions. This procedure is not unlike measuring the strength and direction of an ocean’s current by monitoring the time it takes a swimmer to move across the water—currents moving against the swimmer will result in slower times while those going in the same direction will produce faster times, with stronger and weaker currents enhancing or diminishing the impact on the swimmer.

What they found significantly departed from existing theory--specifically, the speed of the Sun’s plasma motions were approximately 100 times slower than scientists had previously projected.

“Our current theoretical understanding of magnetic field generation in the Sun relies on these motions being of a certain magnitude,” explained Shravan Hanasoge, an associate research scholar in geosciences at Princeton University and a visiting scholar at NYU’s Courant Institute of Mathematical Sciences. “These convective motions are currently believed to prop up large-scale circulations in the outer third of the Sun that generate magnetic fields.”

“However, our results suggest that convective motions in the Sun are nearly 100 times smaller than these current theoretical expectations,” continued Hanasoge, also a postdoctoral fellow at the Max Plank Institute in Katlenburg-Lindau, Germany. “If these motions are indeed that slow in the Sun, then the most widely accepted theory concerning the generation of solar magnetic field is broken, leaving us with no compelling theory to explain its generation of magnetic fields and the need to overhaul our understanding of the physics of the Sun’s interior.”

http://arxiv.org/pdf/1206.3173.pdf

Anomalously Weak Solar Convection
Convective velocities are 20-100 times weaker than current theoretical estimates. This suggests the prevalence of a di different paradigm of turbulence from that predicted by existing models, prompting the question: what mechanism transports the heat flux of a solar luminosity outwards? Advection is dominated by Coriolis forces for wavenumbers ` < 60, with Rossby numbers smaller than  102 at r=R = 0:96, suggesting that the Sun may be a much faster rotator than previously thought, and that large-scale convection may be quasi-geostrophic. The fact that iso-rotation contours in the Sun are not co-aligned with the axis of rotation suggests the presence of a latitudinal entropy gradient.
 

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  • #2
Dotini
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Some seriously interesting and provocative stuff is being brought up here.

NASA is thoroughly on record as saying that the solar magnetic field is key to studying and understanding almost all of its Big Questions - coronal heating process, nature of solar flares, origin of sunspot cycle - about these and other continuously varying characteristics of the sun.

For a relatively new science, helioseismology, to come along and challenge the well-accepted dynamo model of the origin of the solar magnetic field is a big deal to my tiny mind.

Before the mainstream goes dashing off the reservation into alternative hypotheses, I'd expect a lengthy period of skepticism and confirmation with respect to the findings of helioseismologists. After all, helioseismology, the study of moving lumps and bumps on the sun, is not too far removed from phrenology, the discredited science of studying lumps and bumps on the human head! (Please forgive my corny joke) :)

Respectfully submitted,
Steve
 
  • #3
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For a relatively new science, helioseismology, to come along and challenge the well-accepted dynamo model of the origin of the solar magnetic field is a big deal to my tiny mind.
I don't think that any of this challenges the dynamo model. The dynamo model is a very, very basic explanation for how an astrophysical object could generate a magnetic field, but it's a basic framework, and no one knows the exact details.

We don't know why the sun has an 11 year sunspot cycle.

Before the mainstream goes dashing off the reservation into alternative hypotheses, I'd expect a lengthy period of skepticism and confirmation with respect to the findings of helioseismologists.
There is no "mainstream hypothesis". Just a vague framework without any details.

Also, as with most press releases, it's really hard to see what the authors are claiming. I very, very seriously doubt that they are arguing that the solar magnetic field can't come from a dynamo effect. More likely they are claiming that a specific version of the dynamo theory is incorrect. I can't tell this from the paper because it doesn't have any information on it.

They don't mention magnetic fields in the paper. They mention mixing length theory, but mixing length theory is one of those "we know it's wrong, but we don't have the data to do anything better" theories of convection.

The other thing is that people take heliosesmology very, very seriously since the results are extremely well grounded. One of the big triumphs of helioseismology involved the solar neutrino problem. We see fewer neutrinos then we expect. Either there is something strange about the sun or there is something strange about neutrino. The helioseismology people were able to establish that there wasn't anything weird about the sun (as far as temperature goes) so it turned out that neutrinos were weird.
 
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Attached is a link to Livingston and Penn's data updated to July, 2012.

http://www.leif.org/research/Livingston and Penn.png

As they note in their paper there are no sunspots with a magnetic field strength less than around 1500 gauss. Specifically what will happen next is not known.

Will the magnetic field strength of individual sunspots continue to decline or does the mechanism reach a plateau?

Is it possible to interrupt the solar magnetic cycle? If so, how does the cycle restart?

It make take a number of months or years to answer these questions. I will update this thread if there is any significant solar change or new papers related to this subject.
 
  • #5
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On the Origin of Solar and Stellar Magnetic Fields

There is recent evidence that the solar magnetic cycle has been interrupted.
I went to http://arxiv.org/abs/1009.0784 and don't agree with that.

The period of the solar magnetic cycle has not changed, so as far as I'm concerned the cycle hasn't been interrupted. What they are saying is that the magnetic fields of sunspots are weaker. If the fields get below 1500 gauss then the sunspots will still be there, they just won't be visible. It is not clear what at all this means, and there is no particular reason to worry about it.

If convective currents are 1/100 of what was thought, then they've got some rethinking to do. It is pretty difficult to figure out what is going on in the interior of the sun. We don't even have all that great of an idea what is going on in the interior of the Earth.


As to the solar cycle I thought it was reasonably well understood. (I don't feel I have time right now to share my understanding, should I dare call it that.) What is not understood at all are longer cycles of the Sun, like the so-called Little Ice Age. It is a complicated system, that's all I can say.
 
  • #6
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In reply to ImaLooser.

I went to http://arxiv.org/abs/1009.0784 and don't agree with that.

The period of the solar magnetic cycle has not changed, so as far as I'm concerned the cycle hasn't been interrupted. What they are saying is that the magnetic fields of sunspots are weaker. If the fields get below 1500 gauss then the sunspots will still be there, they just won't be visible. It is not clear what at all this means, and there is no particular reason to worry about it.
betzalel. There are different theories as to what forms the magnetic ropes that rise up through the convection zone to form sunspots on the surface of the sun. Eugene Parker hypothesized that the magnetic ropes require a minimum field strength to resist the turbulent forces in the convection zone. It may take a number of months, however, to determine what will or will not happen based on linearly extrapolating the trend for the last 8 years.
If convective currents are 1/100 of what was thought, then they've got some rethinking to do. It is pretty difficult to figure out what is going on in the interior of the sun. We don't even have all that great of an idea what is going on in the interior of the Earth.
betzalel. Let's assume the convection currents are 1/100 which requires a new mechanism to create the solar magnetic field. Earth based observational evidence appears to support the assertion that the solar magnetic cycle is from time to time interrupted (Burn marks on the surface of the planet, abrupt changes to the geomagnetic field, and sudden increase volcanic activity which correlate with cosmogenic isotope changes that caused by solar magnetic cycle changes. Cyclic abrupt climate changes also correlate with the same suite of changes. The Younger Dryas for example.). The restart of the solar magnetic cycle causes abrupt changes to the geomagnetic field and magnetic fields of the other planets. If the sun is the cause of the cyclic geomagnetic excursions there is a new mechanism associated with the sun and one would assume stars of the same origin as the sun.
 
  • #7
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In reply to ImaLooser.

cosmogenic isotope changes

Interesting stuff. that.
 
  • #8
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Attached is a link to Livingston and Penn's data updated to July, 2012.

http://www.leif.org/research/Livingston and Penn.png

As they note in their paper there are no sunspots with a magnetic field strength less than around 1500 gauss. Specifically what will happen next is not known.

Will the magnetic field strength of individual sunspots continue to decline or does the mechanism reach a plateau?

Is it possible to interrupt the solar magnetic cycle? If so, how does the cycle restart?

It make take a number of months or years to answer these questions. I will update this thread if there is any significant solar change or new papers related to this subject.
The following is an update of solar magnetic cycle 24.

Jan Alvestad a long time solar observer is predicting that the solar cycle 24 maximum will be 66.9 and that the solar maximum occurred February, 2012.

See monthly solar cycle data in this link.

http://www.solen.info/solar/

The northern solar magnetic field has changed polarity which indicates that there will be few or no sunspots produced in the solar northern hemisphere based on past observations.
The southern solar magnetic field has not changed polarity. Some predict that the solar southern hemisphere will change polarity in 2014.


The following is a graphical comparison of solar cycle 21, 22, 23, and 24.
http://www.solen.info/solar/cyclcomp.html [Broken]

The solar wind speed is anomalously low. If I remember correctly there was a theoretical calculation that indicated the minimum possible solar wind speed is 300 km/hr. During the solar cycle 23/24 minimum the average solar wind speed dropped below 300 km/hr.

It will be interested to see how low the solar wind speed drops to as solar cycle 24 ends.

The geomagnetic field was quiet to unsettled on October 3. Solar wind speed at SOHO ranged between 276 and 352 km/s.
 
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