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A new double dynamo theory to explain the Sun’s solar cycle

A team of solar scientists have proposed a new theory that they think explains the ebb and flow of the Sun’s eleven year solar cycle, and if right can explain the periodic occurrence of grand minimums where there are essentially no sunspots for decades, such as the Maunder Minimum in the 1600s.

The theory proposes that the Sun has two different dynamos that produce different magnetic waves in its interior. Like waves that can either cancel each other out or combine for more power, these two dynamos do the same over time and thus effect the Sun’s sunspot/solar cycle.

“We found magnetic wave components appearing in pairs, originating in two different layers in the Sun’s interior. They both have a frequency of approximately 11 years, although this frequency is slightly different, and they are offset in time. Over the cycle, the waves fluctuate between the northern and southern hemispheres of the Sun. Combining both waves together and comparing to real data for the current solar cycle, we found that our predictions showed an accuracy of 97%,” said Zharkova.

Zharkova and her colleagues derived their model using a technique called ‘principal component analysis’ of the magnetic field observations from the Wilcox Solar Observatory in California. They examined three solar cycles-worth of magnetic field activity, covering the period from 1976-2008. In addition, they compared their predictions to average sunspot numbers, another strong marker of solar activity. All the predictions and observations were closely matched.

Looking ahead to the next solar cycles, the model predicts that the pair of waves become increasingly offset during Cycle 25, which peaks in 2022. During Cycle 26, which covers the decade from 2030-2040, the two waves will become exactly out of synch and this will cause a significant reduction in solar activity.

“In cycle 26, the two waves exactly mirror each other – peaking at the same time but in opposite hemispheres of the Sun. Their interaction will be disruptive, or they will nearly cancel each other. We predict that this will lead to the properties of a ‘Maunder minimum’,” said Zharkova. “Effectively, when the waves are approximately in phase, they can show strong interaction, or resonance, and we have strong solar activity. When they are out of phase, we have solar minimums. When there is full phase separation, we have the conditions last seen during the Maunder minimum, 370 years ago.”

And on this same subject, last week NOAA posted its monthly update of the solar cycle, showing the Sun’s sunspot activity in June. As I have done every month since 2010, I am posting it here, below the fold, with annotations to give it context.

June 2015 Solar Cycle graph

The graph above has been modified to show the predictions of the solar science community. The green curves show the community’s two original predictions from April 2007, with half the scientists predicting a very strong maximum and half predicting a weak one. The red curve is their revised May 2009 prediction.

In June sunspot activity dropped as the ramp down to solar minimum continued. As I have noted previously, the ramp down so far appears to be taking place faster than in past cycles. In addition, the overall sunspot activity for this solar maximum continues to be far below the predicted numbers. Hopefully, this new double dynamo theory will offer scientists a better tool for understanding what is happening, and maybe even explain the occurrence of the grand minimums that take place every 500 to 1000 years.

Understanding this process is quite critical, as it seems to have an effect on the ebbs and flows of the Earth’s climate. During the Maunder Minimum in the 1600s the Earth experienced what is called the Little Ice Age, when there were crop failures in some years because things never got warm enough to grow crops. If we should experience a Grand Minimum in the coming decades, as this double dynamo theory predicts, than we might be facing another period of colder temperatures. And if so, I think we might wish we had some global warming to counter the cold.

Then again, no one as yet understands the connection between the Sun’s solar cycle and the climate. Nor is this new theory as yet proven. We must remind ourselves always of the uncertainties of science, and take what we learn carefully with a grain of salt.

Genesis cover

On Christmas Eve 1968 three Americans became the first humans to visit another world. What they did to celebrate was unexpected and profound, and will be remembered throughout all human history. Genesis: the Story of Apollo 8, Robert Zimmerman's classic history of humanity's first journey to another world, tells that story, and it is now available as both an ebook and an audiobook, both with a foreword by Valerie Anders and a new introduction by Robert Zimmerman.

The ebook is available everywhere for $5.99 (before discount) at amazon, or direct from my ebook publisher, ebookit. If you buy it from ebookit you don't support the big tech companies and the author gets a bigger cut much sooner.

The audiobook is also available at all these vendors, and is also free with a 30-day trial membership to Audible.

"Not simply about one mission, [Genesis] is also the history of America's quest for the moon... Zimmerman has done a masterful job of tying disparate events together into a solid account of one of America's greatest human triumphs."--San Antonio Express-News


  • Cotour

    Are they able to explain how the level of carbon in earths atmosphere regulates this cycle?

  • Phill O

    Yah right!

    Very interesting data and a great time to prove the theory! Hope I am around for 26.

  • Elmet

    What about Svensmark’s cloud theory? This explains the connection between solar activity and global earth temperatures.

    In essence, higher solar activity means a stronger magnetic field in the solar system which prevents more cosmic rays from reaching the earth. Cosmic rays have been shown to be key catalysts in formation of low level clouds. More cloud cover means lower global temperatures as more of the sun’s radiation is reflected back into space.

    Svensmark’s theory is much more compelling, and backed by quite a bit of evidence, than the CO2 greenhouse gas theory which is supported only by limited data sets or climate models. Of course, models are not proof.

  • katesisco

    I very much like this theory as I see the dynamos as being ‘recharged’ by the high energy cloud NASA says we are in. As this high energy is evident in the other stellar bodies of our system, and not, so far, in our sun, Sol, it has to be going somewhere.
    What if this ‘high energy’ is a surrounding field of a dwindling magnetar? Otherwise known as red/brown dwarf. Or perhaps we have entered the area controlled by a double/triple star system? After all, the ancients were studying the Algol system possibly from the mountains of Ethiopia at Axum.
    Lots of wonderful questions and none of them have to do with gravity.

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