Fig. 1

Solar variability and 27-day periodicity. a The fluxes at Lyman-α (121.6 nm) and 205 nm during the ascending solar cycle 24 at 1 a.u. The Sun was quiet in 2008/2009 and shows increasing activity until 2014. b The relative flux variations at the 27-day periodicity for quiet and active Sun conditions. The presented solar data measured by the SORCE experiment (Lean et al. 2005) (black) and the derived low-pass-filtered fluxes (red) were used for the SV- and nSV-simulation, respectively