Upper panel: distribution of ratios between Hα and Ca II rms emissions, r_LT (black), and r_ST (green). The last one can reach values up to 7.1, but the plot has been cut to ratios of at most 4 for clarity, as there are very few stars with a higher ratio. Middle panel: ST rms ratio versus LT rms ratio (for stars common to the two subsamples), for stars with high LT Ca amplitude (rms > 0.01, filled circles), and stars with a lower LT variability (open circles). The dashed line is the y = x line. Lower panel: same for stars in category #1 (stars), category #2 (diamonds), and category #3 (triangles). The Sun is indicated by the red star.