Noise characterization of the Planck LFI 70 GHz radiometers; 20M (top left), 20S (top right); 21M (bottom left), and 21S (bottom right). For each radiometer, the top figure shows distributions of noise parameters PSD, ξⁿ = {σ₀, f_knee, α}, averaged over all Gibbs samples for the full mission. The bottom figure shows the time evolution of the posterior mean of the noise parameters, and the bottom panel shows the evolution in reduced normalized χ² in units of σ. Black dashed curves and crosses show corresponding values as derived by, and used in, the official Planck LFI DPC pipeline.