Gaussian process regression applied to the longitudinal field. Top: corner plot display of the 2D posterior distributions of the hyperparameters of the GP model (see Eq. (3)) as well as the 1D marginalised distributions along the diagonal. Vertical solid lines indicate the median of the distribution, while dashed lines indicate the 16th and 84th percentiles. Bottom: GP model overplotted to the time series of B_l values and residuals of the model. The shaded area indicates the 1σ uncertainty region.