Diagnostic plots of the solar model and of the α Cen A model. From top to bottom: diagnostic plots of the solar model by neglecting the surface effects, using the Ball & Gizon (2014) surface effect prescription, and using a sixth-order polynomial for the surface effects; and diagnostic plots of α Cen A using the Ball & Gizon (2014) prescription. Left column: fit of the target function by the averaging kernel. Central column: inversion coefficients. Right column: lag plot of the inversion coefficients. The points in red are the values that were excluded.