Fig. 1
Top: daily (dots) and smoothed (bold line) Wolf number over solar cycle 23. Middle: same smoothed Wolf number (black line), and when randomly adding a second-order polynomial dispersion (red dots). Bottom: power spectra of the observed daily (black) and simulated (red) Wolf numbers (respectively R and R′). The solar rotation period (blue solid line) and its first harmonic (blue dashed line) are also shown for comparison.
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