Comparison of the effect of time-lags on the vertical profiles of α dynamo coefficients for Pm = 4 (top) and Pm = 90 (bottom). The purple curves correspond to the α_yx component, and the red curves to α_yy (compensated by a factor of five to make the coefficients easier to compare). Solid lines correspond to the coefficients α computed using the standard IROS method. dashed lines correspond to the instantaneous dynamo coefficients ${\stackrel{\sim }{\alpha }}_{\mathit{ij}}(t\prime =0)$ (i.e., with a time lag of t′=0) using a modified IROS method in which we take into account the time-lag (see text). Finally, dotted lines correspond to the sum of the new coefficients calculated using the modified IROS method from four successive snapshots, namely, ${\displaystyle \sum _{k=0}^4}{\stackrel{\sim }{\alpha }}_{\mathit{ij}}(t\prime =k\mathrm{\Delta }{t}_{\mathrm{snap}})$.