Left panel: the dependency of the V_LT parameter on the solar variability, retrieved from the stellar data. The shaded area indicates the uncertainty (2σ) due to the limited number of stars. The V₁₁ parameter is set to 0.00044 mag. The dashed line corresponds to the expected mean solar variability rms₂₀ = 0.00082. The projection onto V_LT-axis yields the 95% interval for expected long-term variability of the Sun: 0.43% < V_LT < 0.76%. Right panel: the same as the left panel, but the contour calculated with V₁₁ = 0.0002 mag is added. The four dashed lines correspond to four values of expected mean solar variability rms₂₀: 0.00097 mag (no chromospheric secular changes, regression with solid line from Fig. 1), 0.00082 mag (strong chromospheric secular changes, regression with solid line), 0.00065 mag (no chromospheric secular changes, regression with dashed line), 0.00053 mag (strong chromospheric secular changes, regression with dashed line). The projection onto the V_LT-axis yields the interval 0.17% < V_LT < 1.2%.