Exponent of radial profiles of the F-corona calculated with the correlation (corr) and inversion (inv) techniques at r ≥ 3 R_⊙. Top and bottom panels: values obtained for the solar maximum (May and June 2001) and solar minimum (March and April 2008) months, respectively. The best-fitting 1-σ uncertainties are shown by means of the error bars for the correlation method and the width of shaded areas for the inversion method.