Australia: The Land Where Time Began

A biography of the Australian continent 

Solar Activity – A Prediction that it will Decrease by 60% in the 2030s, ‘Mini Ice Age’ Levels Because Sun is Driven by Double Dynamo

Predictions that are unprecedentedly accurate of irregularities within the 11-year cycle of the Sun are produced by a new model of the solar cycle. The model draws on dynamo effects that are located in 2 different layers of the Sun, one near the surface and the other deep in its convection zone. It is suggested by predictions from the model that there will be a decrease of 60 % in solar activity during the 2030s to conditions that were last experienced by the Earth during the mini Ice age that began in 1645.

Professor Valentina Zharkova will present the results at the National Astronomy meeting in Llandudno.

The variation of solar activity that occurs during a cycle lasting 10-12 years was first noticed 172 years ago. It is now known that every cycle is a bit different from the others, and up to the present none of the models of possible causes have fully explained the fluctuations. It has been suggested by many physicists that the cause of the solar cycle is a dynamo resulting from convecting fluid deep within the Sun. It has now been found by Zharkova and her colleagues that if there is a second dynamo that is located close to the surface of the Sun it completes the picture with surprising accuracy.

Zharkova and her colleagues found that magnetic wave components appeared in pairs which originated in 2 different layers of the interior of the Sun. Both have a frequency of about 11 years, though the frequencies of the 2 are slightly out of sync, and they are offset in time. The waves fluctuate between the northern and southern hemispheres of the Sun over a cycle. According to Zharkova when both waves are combined together and the results are compared to real data for the current solar cycle the predictions made by Zharkova and her team showed an accuracy of 97 %.

The model of Zharkova et al. was derived by the use of a technique called ‘principal component analysis’ of the magnetic field observations from the Wilcox Solar Observatory in California. They studied magnetic field activity from 3 solar cycles which covered a period from 1976 to 2008. They also compared their predictions to the average numbers of sunspots, which is another strong marker of solar activity and all the predictions and observations matched closely.

The model suggests that in the next solar cycles the pair of waves will become increasingly offset during Cycle 25, which peaks in 2022, and then in Cycle 26 which covers the decade from 2030-2040, the 2 waves will be directly out of sync and the result of this will be a significant reduction of solar activity.

The 2 waves mirror each other exactly in cycle 26, peaking at the same time but in the opposite hemispheres of the Sun, and at this time their interaction will be disruptive, or they will almost cancel each other out. Zharkova et al. predict that this will lead to the properties of a ‘Maunder Minimum’. Effectively, the waves can show strong interaction when they are approximately in phase, or resonance, and the result is strong solar activity. Solar minimums occur when they are out of phase. The conditions that last occurred in the Maunder minimum 370 years ago are seen when there is full phase separation.

Sources & Further reading

Royal Astronomical Society (RAS). "Solar activity predicted to fall 60% in 2030s, to 'mini ice age' levels: Sun driven by double dynamo." ScienceDaily. ScienceDaily, 9 July 2015. <www.sciencedaily.com/releases/2015/07/150709092955.htm>.