Panel a: three-month moving averaged reconstructed total magnetic flux (thick black line) compared to the averages of the three observational data sets (thick red line). The three individual observational data sets are WSO (squares), KP NSO (diamonds), and MWO (triangles). The reconstructed total magnetic flux shown is ϕ_tot = ϕ_act + 0.4ϕ_eph + ϕ_open, to take the unresolved magnetic flux in small ephemeral regions into account (see Sect. 2.2.3). Panel b: yearly averaged reconstructed OMF (solid line) since 1845 and the reconstruction from the aa-index by Lockwood et al. (2014a, dashed line).