Solar Cycle & Explanation for Recent Changes?

[William Astley]

Is the Sun heading towards a Maunder Minimum?

http://science.nasa.gov/headlines/y2006/10may_longrange.htm[/URL]

The following is an excerpt from the above link:

The sun's "Great Conveyor Belt"
[QUOTE] "Normally, the conveyor belt moves about 1 meter per second—walking pace," says Hathaway. "That's how it has been since the late 19th century." In recent years, however, the belt has decelerated to 0.75 m/s in the north and 0.35 m/s (has recently slowed down to 0.25 m/s – my comment) in the south. "We've never seen speeds so low."
[/QUOTE]

And from the next link, it appears there was a failed solar magnetic field reversal.

[PLAIN]http://science.nasa.gov/headlines/y2006/15aug_backwards.htm[/URL]

Incidentally, Solar Activity in the 20th century was the highest in 8,000 years:

[url]http://cc.oulu.fi/~usoskin/personal/nature02995.pdf[/url]

There was a Doubling of the Sun’s Coronal Magnetic Field in the last 100 years.

http://www.nature.com/nature/journal.../399437a0.html
[QUOTE] The solar wind is an extended ionized gas of very high electrical conductivity, and therefore drags some magnetic flux out of the Sun to fill the heliosphere with a weak interplanetary magnetic field1,2. Magnetic reconnection—the merging of oppositely directed magnetic fields—between the interplanetary field and the Earth's magnetic field allows energy from the solar wind to enter the near-Earth environment. The Sun's properties, such as its luminosity, are related to its magnetic field, although the connections are still not well understood3,4. Moreover, changes in the heliospheric magnetic field have been linked with changes in total cloud cover over the Earth, which may influence global climate5. Here we show that measurements of the near-Earth interplanetary magnetic field reveal that the total magnetic flux leaving the Sun has risen by a factor of 1.4 since 1964: surrogate measurements of the interplanetary magnetic field indicate that the increase since 1901 has been by a factor of 2.3. This increase may be related to chaotic changes in the dynamo that generates the solar magnetic field. We do not yet know quantitatively how such changes will influence the global environment.
[/QUOTE]

And based on proxy data, the sun appears to vary cyclically.
[url]http://www.essc.psu.edu/essc_web/seminars/spring2006/Mar1/Bond%20et%20al%202001.pdf[/url]

Has anyone reviewed the results from the Wilson H-K study, where astronomers examined 70 solar like stars, to determine if stars varied cyclically?

 

[Astronuc]

Based on history, there could be another minimum coming up during the next 100-200 years, but it would not necessarily be as low as the Maunder minimum, although it could be. Don't forget the other recent minimums, Dalton, Spörer, Wolf, Oort, and perhaps hundreds before that.

Apparently we are at some maximum at the moment.
http://en.wikipedia.org/wiki/Maunder_minimum#Other_observations

http://en.wikipedia.org/wiki/Sporer_Minimum

http://en.wikipedia.org/wiki/Dalton_Minimum

http://en.wikipedia.org/wiki/Cosmogenic#Natural
(Always verify Wikipedia information with alternative and authenticated sources)

A recent solar maximum occurred in 2000, so we should be headed into a local minimum. We might have to wait 3-5 or more decades to know if the intensity of mixima are still increasing or starting to decrease.

http://www.windows.ucar.edu/tour/link=/sun/solar_activity.html&edu=high

http://www.windows.ucar.edu/tour/link=/sun/activity/solar_cycle.html&edu=high

http://www.windows.ucar.edu/tour/link=/sun/images/butterfly_jpg_image.html&edu=high

The good news is that there is a reduction in GCR in our neighborhood.

http://hesperia.gsfc.nasa.gov/sspvse/oral/Ken_McCracken/wintergreen1.pdf

In The Modern Era (Since 1954)

( 1 ) The galactic cosmic ray intensity near Earth has been one of the lowest in the past 1150 years.

( 2 ) The frequency of occurrence of large solar particle events has been low compared to the long term average.

For A Period Similar To 1889 - 1901

( 3 ) The galactic cosmic ray intensity was higher compared to the modern era by factors of:

- 7.0 AT 100 MeV
- 3.5 AT 300 MeV
- 2.25 AT 1.0 GeV.

I guess we just wait a see where things are going.

As of the beginning of March 19, 2007, there were no sunspots on the Sun and no indication of when any activity would be observable. And even on March 20, no sunspots could be observed in the ultraviolet wavelengths of light or even filtered white light. But like storm clouds on a horizon, disturbances above an active region had already begun to come into view on the edge of the Sun in the ultraviolet images from SOHO. Initially, we saw some brightening at the Sun's edge and then, a half a day later or so, loops of particles spiraling above the edge of the Sun could be spotted. At this point, we could foretell what was coming next. By the 21st, an active region itself could be seen as it rotated into view. The extreme ultraviolet images told the tale.

http://sohowww.nascom.nasa.gov/pickoftheweek/ - March 25, 2007

http://sohowww.nascom.nasa.gov/gallery/images.html

 

[William Astley]

Solar Tripping Point Vs Cycle Slow Down?

Hi Astonuc,

Why would the next solar Maunder like minimum be in 100 to 200 years, as opposed to the next cycle? Is there evidence of a tripping point change in the solar cycle, as opposed to a slowing down in the solar cycle? (i.e. A change from one type of solar cycle to another?)

Solar cycle 23 appears to be phased shifted as compared to cycle 21 and 22. See the attached link to a daily solar observation site that also provides a record of solar activity.

http://www.dxlc.com/solar/cyclcomp.html

Also recent solar observations have noted an asymmetry between the solar hemispheres. If this was simply a slowing down in solar activity, would we expect the change would be the same for both hemispheres?

http://sait.oat.ts.astro.it/MSAIt760405/PDF/2005MmSAI..76.1072Z.pdf

From the above referenced paper:

“The statistical results in sunspot and plage … in 1996-2004 reveal a strong North-South asymmetry of about 0.4 and period of about 7 years for sunspots and 0.6 and a period of about 8 years for plages … These asymmetries reflect some essential properties of the global solar activity to be accounted for in the solar dynamo modeling.”

GCR Levels
The reduction of galactic cosmic rays in the vicinity of the Earth is due to the doubling of the solar large scale magnetic field. If the solar activity slows down and the length of solar cycles increases, the solar large scale magnetic field will decrease and GCR intensity will increase. GCR is also reduced by the geomagnetic field.

 

[Astronuc]

Why would the next solar Maunder like minimum be in 100 to 200 years, as opposed to the next cycle? Is there evidence of a tripping point change in the solar cycle, as opposed to a slowing down in the solar cycle?

We have only been doing a detailed study of the sun's energy generation system for about 50 years or so - there were no modern day plasma physicsist around in the 1600's - 1800's, so we don't really know the preceeding conditions leading to these minima. We certainly can see when they start happening, but that takes decades of observing the decreasing number of sunspots.

The peak-to-peak period is about 200 years between maxima based on radiocarbon. So the sun could start a drop toward a new minimum, but we won't know for a while if it is a shallow (Oort or Dalton min) or deep (Maunder or Spörer). If the next minimum occurs on the same schedule as the previous, then perhaps we will know in 100 year how significant it will be - but we won't be around for it - but out grandchildren or great grandchildren will be.

Then again, looking at the current solar maximum, it is greater than the one 1000 years ago, so perhaps the maximum could continue for the next cycle or so.

I plan to contact some colleagues at NASA who model solar activity and GCR with respect to the conditions associated with decreasing solar activity, and I want to follow up on some of the other questions and links.

 

[ray b]

how do spots or the lack of sun spots relate to energy out put and Earth temps
as I understand it, spots are cooler but avg total sun surface temps go up making for more heat
or do we get our heat from the outer bits of the solar atmosphere or the surface

 

[Astronuc]

how do spots or the lack of sun spots relate to energy out put and Earth temps

That's what a lot of people would like to know. Looking at the spots - they represent a small fraction, ~ <1% of the projected area.

In addition to the photoelectric spectrum, there is the interaction of the 'solar wind' and GCR which may (or may not) have a significant impact on the weather.

Perhaps an answer would be found in correlating auroral activity (in addition to sunspots) with cold/hot cycles of the earth.

I want to look into the "results from the Wilson H-K study, where astronomers examined 70 solar like stars, to determine if stars varied cyclically", which William mentioned. Ostensibly stars do vary cyclically like the sun, but perhaps with different fequencies and intensities. However, how would one observe starts where sunspots are not 'discernable'. I am wondering spectroscopically - which begs me to ask if the solar cycle has been correlated with changes in emission/absorption line intensities.

 

[William Astley]

Solar Cycle & Solar Variability

The following is from a solar review article write by a solar research team. The article summarizes at a high level current solar research findings and understanding. It includes a list of basic questions that this solar research project hopes to answer.


http://sdo.gsfc.nasa.gov/sdo_sdt_report.doc

From page 4-5

“Solar magnetic fields with their associated forces and electric currents are recognized as being responsible for the Sun’s activity, but the underlying process which create …are poorly understood. Although helioseismology has revealed flows and thermal structures related to magnetic variability, present theoretical models based on these observations can only broadly reproduce the observed magnetic evolution and are far from having predictive capability.”

“Historical records suggest that the strength of the cyclic magnetic variations may have been different than today and that there may have been associated terrestrial climate changes. Furthermore, sun-like stars are observed to have a wider range of activity than is seen in the Sun, suggesting that current solar behaviour could be misleadingly steady.”

From page 21

“The solar cycle has proven to be notoriously difficult to predict. Once a cycle is well under way its smoothed behaviour can be predicted with some reliability using statistical models for the shape of the curve. Predictions prior to the start of cycle are, however, much less reliable and longer range predictions are virtually useless. Currently all methods of cycle prediction are empirical in nature. While we understand many of the processes involved in producing the solar cycle we do not have a physical model that will take initial conditions and predict future behaviour.”

 

[William Astley]

Recent Solar Variability and Planetary Temperature

There is significant data and supporting analysis that has been published in the last five years to support the hypothesis that solar variability and geomagnetic field changes are the principal cause of past large scale climate changes. As this paper notes, however, the mechanism is more complicated than a simple linear relationship to number of sunspots. See figure 6 in the attached paper that shows there is close correlation between observed global temperature anomalies and the solar index "ak".

I found this article also interesting as it notes the 20th century solar changes are very unusual.

Paper by Georgieva, Bianchi, & Kirov “Once again about global warming and solar activity”

http://sait.oat.ts.astro.it/MSAIt760405/PDF/2005MmSAI..76..969G.pdf

From above linked paper

"It has been noted that in the last century the correlation between sunspot number and geomagnetic activity has been steadily decreasing from - 0.76 in the period 1868-1890 to 0.35 in the period 1960-1982, ... According to Echer et al (2004), the probable cause seems to be related to the double peak structure of geomagnetic activity. The second peak, related to high speed solar wind from coronal holes (my comment: For example coronal hole 254 that produced the Dec 16, 2006 peak in solar wind, during a sun spot minimum, see link to Solar Observation Data, in my other comment.), seems to have increased relative to the first one, related to sunspots (CMEs) but, as already mentioned, this type of solar activity is not accounted for by sunspot number. In figure 6 long term varations in global temperature are compared to the long-term variations in geomagnetic activity as expressed by the ak-index (Nevanlinna and Kataga 2003). The correlation between the two quantities is 0.85 with p< 0.01."

 

[William Astley]

Hypothesis, Doubling of Sun's Large Magnetic Field

Attached below is a paper that provides a hypothesis for why the solar large scale magnetic field has more than doubled in the 20 th century.

The following is an excerpt from the paper: "Evolution of the Sun's large-scale magnetic field since the Maunder minimum"

http://www.nature.com/nature/journal/v408/n6811/abs/408445a0.html

A part of the Sun's magnetic field reaches out from the surface into interplanetary space, and it was recently discovered3 that the average strength of this interplanetary field has doubled (my comment. 2.3 times) in the past 100 years. There has hitherto been no clear explanation for this doubling. Here we present a model describing the long-term evolution of the Sun's large-scale magnetic field, which reproduces the doubling of the interplanetary field. The model indicates that there is a direct connection between the length of the sunspot cycle and the secular variations.

 

[William Astley]

Sun is spotless. Implications?

As can be seen in the attached link to a daily solar observatory, the sun is currently spotless. That link provides daily and monthly solar data. As can be seen in the table “Monthly Solar Data”, the solar magnetic cycle appears to be currently unstable, based on the monthly changes in the number of sun spots. (The number of sunspots is an indication of how the solar magnetic cycle is progressing.)

Link to Daily and Monthly Solar Terrestrial Activity Data:

http://www.dxlc.com/solar/

The solar monthly sunspot number dropped to 4.9 in February 2006, which was a minimum for solar cycle 23. The monthly sunspot number then increased from the February, 2006 cycle 23 minimum of 4.9 to 30 in April 2006. It appears solar cycle 24 failed to start as the number of monthly sun spots dropped from 30 in April 2006, to 12 in July, 2006 and then increased to 21 November, 2006. The number of monthly sunspots dropped from 21 in November 2006 and was 4.8 for the month of March, 2007.

 

[William Astley]

What Causes the Solar Cycle?

I am interested in what event precipitates a change in the solar cycle from normal cycle to Maunder like minimum. The following is what I have found concerning "What Causes the Solar Cycle?"

From Jack Zirker's book "Journey from the Center of the Sun" Princeton Science Library. Zirker's book is a summary of recent solar observations and theories. There is a significant number of fundamental solar processes that are not understood.

The sun is a magnetic star. The sun spots have very strong magnetic fields associated with them (around 3000 gauss, the Earth's magnetic field is around 0.5 gauss.). The strong magnetic fields move to the sun's surface and are then removed as part of the solar cycle. As there is not sufficient time during the 11 year long solar cycle, to generate such strong magnetic fields, in the solar convection zone, the sun spot magnetic fields cannot be generated in the solar convection zone. The following is Zirker's description of the problem and the current theory as to where the strong solar magnetic field is generated.

Other problems with solar cycle models began to surface. They centered on those magical magnetic ropes that turn into sunspots. As we know, the field strength in a large sunspot can reach 3,000 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 ...the buoyant rope would rise through the convection zone in much less time than 11 years. ...(Solution. my comment) Several theorists had pointed out that the ideal place to store a magnetic rope was just beneath the convection zone, at the bounder with the radiative zone. Convection motions would overshoot the bounder slightly, push down on a buoyant rope, and keep it submerged almost indefinitely. The field there could reach 100,000 gauss with bobbing up.

Based on this mechanism, a Maunder minimum could be triggered by the larger planets moving the solar core and radiative zone, separating it from the convection zone. The magnetic field then would build up in the radiative zone but not rise to the surface of the sun.

Interesting super solar flares (X flares) have been observed during recent solar minimums. Very, very high stellar flares has been observed for other solar like stars (as part of the Wilson H-K and other similar studies where the objective is to study other stars to see how the stellar cycle varies.) when the star in question was during a minimum.

I am also interested in the magnitude and periodicity of super solar flares as there is geological evidence of residual that could be cause by a super solar flare. The residual appears to coincide with geomagnetic field minimums and reversals

 

[Astronuc]

NOAA ANNOUNCES NEXT SOLAR STORM CYCLE WILL LIKELY START NEXT MARCH
http://www.noaanews.noaa.gov/stories2007/s2847.htm

April 26, 2007 — The next 11-year cycle of solar storms will most likely start next March and peak in late 2011 or mid-2012—up to a year later than expected—according to a forecast issued by the NOAA Space Environment Center in coordination with an international panel of solar experts. The NOAA Space Environment Center led the prediction panel and issued the forecast at its annual Space Weather Workshop in Boulder, Colo. NASA sponsored the panel.

Expected to start last fall, the delayed onset of Solar Cycle 24 stymied the panel and left them evenly split on whether a weak or strong period of solar storms lies ahead, but neither group predicts a record-breaker.

During an active solar period, violent eruptions occur more often on the sun. Solar flares and vast explosions, known as coronal mass ejections, shoot energetic photons and highly charged matter toward Earth, jolting the planet's ionosphere and geomagnetic field, potentially affecting power grids, critical military and airline communications, satellites, Global Positioning System (GPS) signals, and even threatening astronauts with harmful radiation. These same storms illuminate night skies with brilliant sheets of red and green known as auroras, or the northern or southern lights.

In the cycle forecast issued Wednesday, half of the panel predicts a moderately strong cycle of 140 sunspots, plus or minus 20, expected to peak in October 2011. The other half predicts a moderately weak cycle of 90 sunspots, plus or minus 10, peaking in August 2012. An average solar cycle ranges from 75 to 155 sunspots. The late decline of Cycle 23 has helped shift the panel away from its earlier leaning toward a strong Cycle 24. Now the group is evenly split between strong and weak.

The first year after solar minimum, marking the end of Cycle 23, will provide the information scientists need to arrive at a consensus. . . .

 

[William Astley]

Maunder Minimum?

A Maunder Minimum has predicted in the following paper based on solar observations in 2003, by the authers who used a physical solar model. (See link for details.)

Comment:
The sun is currently not following the expected solar cycle behaviour. The NASA solar cycle prediction group are planning to meet every 3 months to re-evaluate the cycle 24 prediction based on new data.

http://adsabs.harvard.edu/abs/2003SPD...34.0603S

Long-range (few years to decades) solar activity prediction techniques vary greatly in their methods. They range from examining planetary orbits, to spectral analyses (e.g. Fourier, wavelet and spectral analyses), to artificial intelligence methods, to simply using general statistical techniques. Rather than concentrate on statistical/mathematical/numerical methods, we discuss a class of methods which appears to have a "physical basis." Not only does it have a physical basis, but this basis is rooted in both "basic" physics (dynamo theory), but also solar physics (Babcock dynamo theory). The class we discuss is referred to as "precursor methods," originally developed by Ohl, Brown and Williams and others, using geomagnetic observations.

My colleagues and I have developed some understanding for how these methods work and have expanded the prediction methods using "solar dynamo precursor" methods, notably a "SODA" index (SOlar Dynamo Amplitude). These methods are now based upon an understanding of the Sun's dynamo processes- to explain a connection between how the Sun's fields are generated and how the Sun broadcasts its future activity levels to Earth. This has led to better monitoring of the Sun's dynamo fields and is leading to more accurate prediction techniques. Related to the Sun's polar and toroidal magnetic fields, we explain how these methods work, past predictions, the current cycle, and predictions of future of solar activity levels for the next few solar cycles.

The surprising result of these long-range predictions is a rapid decline in solar activity, starting with cycle #24. If this trend continues, we may see the Sun heading towards a "Maunder" type of solar activity minimum - an extensive period of reduced levels of solar activity. For the solar physicists, who enjoy studying solar activity, we hope this isn't so, but for NASA, which must place and maintain satellites in low Earth orbit (LEO), it may help with reboost problems. Space debris, and other aspects of objects in LEO will also be affected.

 

[William Astley]

More analysis supporting a Solar Cycle Change

The following is a 2004 paper that predicts the sun is heading towards a Maunder Minimum based on an analysis of the paleo record of solar activity.

http://adsabs.harvard.edu/abs/2004ApJ...605L..81B

We have examined the long-term trends in the solar variability that can be deduced from some indirect data and from optical records. We analyzed the radiocarbon measurements for the last 4500 years, based on dendrochronology, the Schove series for the last 1700 years, based on auroral records, and the Hoyt-Schatten series of group sunspot numbers. Focusing on periodicities near one and two centuries, which most likely have a solar origin, we conclude that the present epoch is at the onset of an upcoming local minimum in the long-term solar variability. There are some clues that the next minimum will be less deep than the Maunder minimum, but ultimately the relative depth between these two minima will be indicative of the amplitude change of the quasi-two-century solar cycle.