Artificial time series for an oscillation with a period of 82 days, a damping time τ_d of 60 yr, and a sampling‐time interval Δt of 20 days, computed according to eq. (3). The top panel shows the computed time series that, as indicated, covers about 1600 yr. In the bottom panel the points show the binned, normalized distribution of mode energy in units of the mean energy; the solid line corresponds to the expected exponential distribution in eq. (1) (for further details, see Chang & Gough 1998).