Abstract
We derive two principal components (PCs) of temporal magnetic field variations over the solar cycles 21–24 from full disk magnetograms covering about 39% of data variance, with σ = 0.67. These PCs are attributed to two main magnetic waves travelling from the opposite hemispheres with close frequencies and increasing phase shift. Using symbolic regeression analysis we also derive mathematical formulae for these waves and calculate their summary curve which we show is linked to solar activity index. Extrapolation of the PCs backward for 800 years reveals the two 350-year grand cycles superimposed on 22 year-cycles with the features showing a remarkable resemblance to sunspot activity reported in the past including the Maunder and Dalton minimum. The summary curve calculated for the next millennium predicts further three grand cycles with the closest grand minimum occurring in the forthcoming cycles 26–27 with the two magnetic field waves separating into the opposite hemispheres leading to strongly reduced solar activity. These grand cycle variations are probed by α − Ω dynamo model with meridional circulation. Dynamo waves are found generated with close frequencies whose interaction leads to beating effects responsible for the grand cycles (350–400 years) superimposed on a standard 22 year cycle. This approach opens a new era in investigation and confident prediction of solar activity on a millenium timescale.
Highlights
Solar activity is manifested in sunspot occurrence on the solar surface characterized by the smoothed sunspot numbers, which were selected as a proxy of solar activity
Magnetic flux tubes seen as sunspots are produced from the solar background magnetic field (SBMF) by a joint action of differential rotation (Ω -effect) and radial shear (α-effect), while the conversion of toroidal magnetic field into poloidal field is governed by the convection in the rotating body of the Sun
The two principal components (PCs) derived from solar background magnetic field (SBMF)[15] and predicted for cycle 24–26 are presented in Fig. 1
Summary
Solar activity is manifested in sunspot occurrence on the solar surface characterized by the smoothed sunspot numbers, which were selected as a proxy of solar activity (see, for example, the top plot in http://solarscience.msfc.nasa.gov/images/bfly.gif). Magnetic flux tubes (toroidal magnetic field) seen as sunspots are produced from the solar background magnetic field (SBMF) (poloidal magnetic field) by a joint action of differential rotation (Ω -effect) and radial shear (α-effect), while the conversion of toroidal magnetic field into poloidal field is governed by the convection in the rotating body of the Sun. The action of the Coriolis force on the expanding, rising (compressed, sinking) vortices results in a predominance of right-handed vortices in the Northern hemisphere and left-handed vortices in the Southern hemisphere leading to the equatorward migration of sunspots during a solar cycle duration visible as butterfly diagams (see http://solarscience.msfc.nasa.gov/images/bfly.gif, the bottom plot)
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