Fig. 1

The scatter plots and linear fits between the Swarm magnetic residuals \(\Delta X\) (red), \(\Delta Y\) (green) and \(\Delta Z\) (blue) and the components \(X_{\mathrm{MMA}}\), \(Y_{\mathrm{MMA}}\) and \(Z_{\mathrm{MMA}}\) of the MMA model of the magnetospheric magnetic field (Sabaka et al. 2020) along Swarm A (top panels), Swarm B (middle panels) and Swarm C (bottom panels) satellite tracks. The results are shown for a moderate magnetic storm of 84,5-h duration from April 11 to April 15, 2014. The Dst index equals \(-81\) at the main phase of the storm. Swarm satellite track numbers are given in the headers of panels. Only data from the mid-latitude interval \(I_{_\mathrm{ML}}^{10^\circ }\), \(I_{_{\mathrm{ML}}}^{10^\circ }=(\vartheta _\mathrm{R_2^n}+10^\circ ,\vartheta _{\mathrm{R_2^s}}-10^\circ )\), are included. A least-squares regression line is shown by black line. The corresponding correlation coefficient (R), regression slope (S) and mean (M in nT) are shown in each panel. In addition, RMSD (in nT) shows the root mean squares of the differences between the MMA and the predicted values from the regression line. For comparison, light-blue line stands for the exact linear relationship between Swarm residuals and a modelled field