Fig. 1.
Sun’s chromospheric activity over 50 years according to Egeland et al. (2017). Upper: complete time series measurements made over 50 years depicting the SMW periodic profile. Bottom: both the Lomb-Scargle (left), and the autocorrelation function (ACF, see Brockwell 2002) (right) periodograms showing the Pcyc ≈ 11 yr solar activity cycle.
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