List of Figures

View Image Figure 1:
13-month sliding averages of the monthly average relative sunspot numbers R (green) and group sunspot numbers RG (black) for the period 1611 – 1998.
View Image Figure 2:
Monthly values of the 10.7 cm radio flux in solar flux units for the period 1947 – 2009. The solar flux unit is defined as 10–22 W/m2 Hz. The green curve shows Rm + 60, where Rm is the monthly mean relative sunspot number. (The vertical shift is for better comparison.) Data are from the NRC Canada (Ottawa/Penticton).
View Image Figure 3:
The variation of the monthly smoothed relative sunspot number R during the period 1749 – 2009, with the conventional numbering of solar cycles.
View Image Figure 4:
Amplitudes of the sunspot cycles (dotted) and their Gleissberg filtered values (blue solid), plotted against cycle number.
View Image Figure 5:
Monthly smoothed sunspot number R at cycle maximum plotted against the rise time to maximum (left) and against cycle length (right). Cycles are labeled with their numbers. In the plots the red dashed lines are linear regressions to all the data, while the blue solid lines are fits to all data except outliers. Cycle 19 is considered an outlier on both plots, cycle 4 on the right hand plot only. The corresponding correlation coefficients are shown.
View Image Figure 6:
Monthly smoothed sunspot number R at cycle maximum plotted against the values of R at the previous minimum (left) and 2.5 years before the minimum (right). Cycles are labeled with their numbers. The blue solid line is a linear regression to the data; corresponding correlation coefficients are shown. In the left hand panel, cycle 19 was considered an outlier.
View Image Figure 7:
Magnetic field strength in the Sun’s polar regions as a function of time. Blue solid: North; red dashed: (− 1)⋅South; thin black solid: average; heavy black solid: smoothed average. Strong annual modulations in the hemispheric data are due to the tilt of the solar equator to the Ecliptic. Data and figure courtesy of Wilcox Solar Observatory (see External Link for updated version).
View Image Figure 8:
Power spectrum of the smoothed monthly sunspot number series for the period 1749 – 2008. Solid vertical bars mark the 11-year period, its first harmonic and subharmonic; dashed vertical bars are drawn at a fiducial period of 14.5 years, its harmonic and subharmonic.
View Image Figure 9:
Pseudo-Wigner power distribution in the sunspot number record, with time on the abscissa and frequency on the ordinate. The three horizontal bands of high power correspond, from bottom to top, to the Gleissberg cycle, the 11-year cycle and its first harmonic. The sunspot number curve is shown on top for guidance (figure courtesy of Z. Kolláth).