A) Probability density function (PDF) of the reconstructed decadal sunspot numbers as derived from the same 106 series as in Fig. 2 (gray-filled curve). The blue curve shows the best-fit bi-Gaussian curve (individual Gaussians with mean/σ being 44/23 and 12.5/18 are shown as dashed blue curves). Also shown in red is the PDF of the historically observed decadal group sunspot numbers (Hoyt & Schatten 1998) (using bins of width ΔS = 10). Vertical dashed lines indicate an approximate separation of the three modes and correspond to ± 1σ from the main peak, viz. S = 21 and 67. Panels B) and C) depict PDFs built in the same way (but from a single mean reconstruction) using dipole moment models based on either the GEOMAGIA (Knudsen et al. 2008) or ArcheoInt (Genevey et al. 2008) intensity databases. Panels D) and E) show PDFs (for the same time-period) inferred from a previous similar reconstruction (Usoskin et al. 2007) using an early dipole moment model (Yang et al. 2000) and from the recent reconstruction of Roth & Joos (2013) using the CALS10k.1b model (Korte et al. 2011), respectively.
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