Schematic showing the geometry of the shock, observers, and particle-filled flux tubes for the cases with (right panel) and without (left panel) corotation after 48 h of shock propagation. Here, x and y are heliocentric cartesian coordinates in the heliographic equatorial plane. Observers A-F are denoted by the coloured circles. The shock’s projection onto the plane is displayed here as the orange shaded segments. The grey IMF lines represent the range of particle-filled flux tubes. The inset shows the range of longitudes that are filled with particles. The solid red curved lines show the IMF lines that are currently connected to the edges of shock. The solid green curved lines show the magnetic flux tubes at the edges of the shock at the initial time. In the corotation case, these have rotated with respect to their initial location, shown by the dashed green line.