Fig. 3

Error growth rates of the numerical geodynamo model. The top panel a shows an example of estimation of error growth rate using least-squares linear regression, where the gray lines denote magnetic errors, \(\Delta y_{l}\) (Eq. 19), for the spherical harmonic degree from 1 to 8, and the blue line is the result of the linear regression. The bottom panel b shows superimposed ten results of estimation of error growth rates, where the average error growth rate turns out to be 187 with 95 percent uncertainty (2σ) of 36. See text for details of the estimation