This figure compares the 3D ballistic propagation without pressure correction (a) and with pressure correction (b), using BATS-R-US data as input, over one Carrington rotation (CR = 2083). The x axis shows Carrington longitude, the y axis shows solar distance, the colorbar shows solar wind speed. In case of the uncorrected propagation, the faster solar wind streams can overtake the slower streams (i.e., around longitude −50° to 0°). During the speed correction, the speed is recalculated to account for this negative effect of the simple ballistic propagation.