Posterior distributions (left) and radial evolution (right) of the standard deviation, σ_δ, the injection scale, ℓ_inj, and the spectral index α of the density fluctuation power spectrum parameters, jointly evaluated on the whole X-COP cluster sample in the four regions as defined in Table (1) and within R₅₀₀. The colour scale matches the four regions of interest, and the turquoise distribution represents the entire R₅₀₀ region. The black dashed line represents the expected 11/3 index from Kolmogorov-Oboukhov theory.