Fig. 5

Power spectra of the RMS error for CHAOS-6 hybrid hindcasts at Earth’s surface over 2010–2015, computed with a the 2001.0–2010.0 and b 2009.0–2010.0 model fitting periods for \(L_u=14\) and \(N=0,1,2\). The value \(N=0\) signifies the absence of any diffusive contribution. Shown for comparison are the error spectra for IGRF-11 and a CHAOS-3 forecast