Comparison of R_i and the F_10.7 proxy for R_i over the last 60 years (Johnson 2010). Top panel: plots of the monthly R_i and F_10.7 values (black and white dots respectively) and of the 1-year smoothed R_i and F_10.7 values (red and blue curves respectively). The cycle numbers are indicated. Bottom panel: monthly ratios R_i/F_10.7 (diamonds) and the 1-year smoothed ratio (solid line) with the 3σ confidence levels (dashed lines). It shows the overall agreement between the indices until the year 2000 and the significant discrepancy appearing after 2000.