Solar Cycle Predictions Based on Extrapolation of Spectral Components: An Update

Three series (1876 – 1986, 1886 – 1996, and 1896 – 2006) of 111 annual values of sunspot number R _z in each were subjected to spectral analysis to detect periodicities by the maximum entropy method (MEM), and the periodicities so obtained were used in a multiple regression analysis (MRA) to estimate the amplitudes and phases. All series showed roughly similar spectra with many periodicities (24 or more), but most of these were insignificant. The significant periodicities (far exceeding 2σ) were near 5, 8 – 12, 18, and 37 years. Using the amplitudes and phases of these, we obtained reconstructed series, which showed good correlations (+ 0.7 and more) with the original series. When extrapolated further in time, the reconstructed series indicated R _z(max) in the ranges 80 – 101 (mean 92) for cycle 24 during years 2011 – 2014, 112 – 127 (mean 119) for cycle 25 during years 2022 – 2023, 115 – 120 (mean 118) for cycle 26 during years 2032 – 2034, and 100 – 113 (mean 109) for cycle 27 during 2043 – 2045.