Australia: The Land Where Time Began

A biography of the Australian continent 

Mini Ice Ages –  Prediction of Solar Activity Cycles on Millennium Time Scale from Principal Component Analysis

According to Zharkova et al. they derived 2 principal components (PCs) of temporal magnetic field variations over solar cycles 21-24 based on full disc magnetograms that covered about 39 % of data variance, with σ = 0.67. These PCs are attributed to 2 main magnetic waves that travelled from opposite hemispheres that had close frequencies and a phase shift that was increasing. They also derived mathematical formulae for these waves using symbolic regression analysis and calculated their summary curve which was shown to be linked to solar activity index. When the PCs were extrapolated backwards for 800 years they revealed 2 350-year grand cycles that were superimposed on 22-year cycles that had the features that showed a remarkable resemblance to the activity of sunspots that had been reported in the past that included the Maunder Minimum and the Dalton Minimum. For the next millennium the summary curve that was calculated predicted a further 3 grand cycles with the closest grand minimum occurring in the forthcoming cycles 26-27 with 2 magnetic field waves that were separated into the opposite hemispheres which led to solar activity that was strongly reduced. The variations of these grand cycles are probed by α – Ω dynamo model with meridional circulation. Dynamo waves were found that had close frequencies with interactions that led to beating effects responsible for the grand cycles (350-400 years) which were superimposed on a standard 22 year cycle. Zharkova et al. say a new era in investigation and confident prediction of solar activity on the timescale of a millennium is opened by this approach.

Sources & Further reading

1. Zharkova, V. V., S. J. Shepherd, E. Popova and S. I. Zharkov (2015). "Heartbeat of the Sun from Principal Component Analysis and prediction of solar activity on a millenium timescale." Scientific Reports 5: 15689.