The residuals (the difference between the observation and the model prediction), calculated every 15 s, are plotted along the track, with positive residuals plotted west of the track (in red) and negative residuals east of the track (in blue) as the spacecraft passes through periapsis from north to south. The radial component of the magnetic field model is shown in the background. The projection is cylindrical with a grid spacing of 15; the equator is highlighted in grey. The residuals are calculated within the box shown in black. The colour scale is linear between the indicated limits and the bar below the colour scale depicts the residual scale. b , The residuals from the 42-orbit steady flow model after applying the pass-by-pass velocity scale factors.
