Are we heading for a Maunder Minimum?

August 7th, 2015, Published in Articles: EngineerIT

 

Will history repeat itself? Is the sun gearing for a Maunder Minimum? Prof. Valentina Zharkova, a mathematics professor at Northumbria University believes we are.  She delivered the results of a study which proved that the sun may have two hearts in a presentation at the Royal Astronomical Society’s National Astronomy meeting, held from 5 to 9 July in Llandudno, Wales, UK.

Comparison of three images over four years apart illustrates how the level of solar activity has risen from near minimum to near maximum in the Sun's 11-years solar cycle. (Picture credit: SOHO/ESA/NASA)

Comparison of three images over four years apart illustrates how the level of solar activity has risen from near minimum to near maximum in the sun’s eleven-year solar cycle. (Picture credit: SOHO/ESA/NASA)

According to NASA a “Maunder Minimum” refers to the seven decades, from 1645 to 1715, when the sun’s surface ceased its heat-releasing magnetic storms and coincided with the Little Ice Age, a period of chillier temperatures, from around 1550 to 1850 in Europe, North America and Asia. It seems to conflict with the reports of global warming.

Our sun has an approximately eleven-year activity cycle. During peak periods, it exhibits lots of solar flares and sunspots. Magnetic bubbles of charged particles (coronal mass ejections) may burst from the surface during this period, streaming material into space. These ejections can affect satellites and powerlines on Earth. During lull periods, such activity may almost stop altogether. But the eleven-year cycle isn’t quite able to predict all of the sun’s behaviour — which can seem erratic at times.

Prof. Valentina Zharkova and her colleagues (Prof. Simon Shepherd of Bradford University, Dr. Helen Popova of Lomonosov Moscow State University, and Dr. Sergei Zarkhov of Hull University) have found a way to account for the discrepancy – a “double dynamo” system.

The sun, like all stars, is a large nuclear fusion reactor that generates powerful magnetic fields, similar to a dynamo. The model developed by Prof. Zharkova’s team suggests there are two dynamos at work in the sun; one close to the surface and one deep within the convection zone. They found this dual dynamo system could explain aspects of the solar cycle with much greater accuracy than before — possibly leading to enhanced predictions of future solar behaviour.

“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 [for both] and they are offset in time,” says  Prof. Zharkova. The two magnetic waves either reinforce one another to produce high activity or cancel out to create lull periods.

Prof.  Zharkova and her colleagues used magnetic field observations from the Wilcox Solar Observatory in California for three solar cycles, from the period of 1976 to 2008. In addition, they compared their predictions to average sunspot numbers — another strong marker of solar activity. All the predictions and observations matched closely. Their predictions using the model suggest an interesting longer-term trend beyond the eleven-year cycle. It shows that solar activity will fall by 60% during the 2030s, to conditions last seen during the Maunder Minimum of 1645 to 1715. “Over the cycle, the waves fluctuate between the sun’s northern and southern hemispheres. Combining both waves together and comparing to real data for the current solar cycle, we found that our predictions showed an accuracy of 97%,” says Prof. Zharkova.

The model predicts that the magnetic wave pairs will become increasingly offset during Cycle 25, which peaks in 2022. Then during Cycle 26, which covers the decade from 2030 to 2040, the two waves will become exactly out of synch, cancelling one another out. 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. We predict that this will lead to the properties of a “Maunder minimum”, says Prof. Zharkova.

If Prof. Zharkova’s predictions come true, users of shortwave for communication will be in for a lean time.

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