tokens: reliable results (e.g., Henry 1999 ). Lastly, the number of genuinely SLS bright enough to measure with modest (meter-class) telescopes is small. As measured by the number of stars in a meaningful volume of hyperspace similar to the Sun (Radick et al. 1998 ), considerable work would be needed to identify new, dimmer targets. There remains the nagging question of whether the Sun is different from other SLS (Gustafsson 1998 ). Radick et al. ( 2018 ) conclude “it may be unusual in two respects: (1) its comparatively smooth, regular activity cycle, and (2) its rather low photometric brightness variation relative to its chromospheric activity level and variation...” These authors speculate that facular brightening may nearly balance sunspot darkening, explaining the second point. Egeland ( 2017 ) pointed out that the Sun has the most regular cycle of all SLS measured so far. The question of whether the Sun acts (magnetically) as other SLS is difficult to answer. If all such stars are indeed magnetically similar, it implies that stars have a consistent magnetic variability over timescales of several Gyr (the age range of our sample) to ∼100 million years. The latter is close to the uncertainty in ages of older main sequence stars obtained using the best available methods. It is impossible to verify or refute the question for the Sun, even using a cosmogenic proxy record, which presently stretches only 0.01 million years into the past (Wu et al. 2018 ). Certainly, the most Sun-like of the stars found so far, 18 Sco (HD 146233) has clear differences in metallicity and starspot cycle length. Nevertheless, there is hope that a carefully selected stellar ensemble can represent the activity of the Sun in middle and old age. van Saders et al. ( 2016 ) demonstrated that rotation rates of middle-aged and old GV stars converge as a result of weakened magnetic breaking. Unlike younger stars, there is perhaps a good physical reason to believe that magnetic dynamos of older Suns, and their effects, should be similar. 3. Time Series from a Solar “Reconstruction” The limits of our analysis due to the lack of longer time series can be illustrated through a comparison of our results with a “reconstruction” of solar variations with extraordinary and significant forcing of ≈6 W m −2 from 1600 to 2010 (Shapiro et al. 2011 ). Figure 5 highlights two extended periods of near-monotonic large changes predicted over 15 and 50 yr. The first is compatible with several stars (HD 126053, 52711, 50692, 143761; Table 2 ). The second (50 yr) period is compatible with about half of the stars listed. Figure 5. Variations from a model by Shapiro et al. ( 2011 ) are shown, in which variations in radiative forcing since 1750 are of the order of 3 W m −2 , far larger than the IPCC estimate of −0.30 to +0.10 W m −2 Myhre et al. ( 2013 ). (The relationship between Strömgren magnitudes and irradiance is linear, taken from the model computations. The factor differs from the values
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