BS width for (a) different SW temperatures (fixed P_d = 1.2 nPa) and (b) different P_d values (fixed T_sw = 1.8 × 10⁵ K) when the SW density increases (fixed the SW velocity to 350 km s⁻¹, red dots) or the SW velocities increases (fixed the SW density to 12 cm⁻³, blue dots). Sun–Earth IMF orientation with |B| = 10 nT. The dashed lines indicate the data fit to the expression . The solid black lines indicate the regression in the simulations with the SW velocity fixed and P_d > 4 nPa and in the simulations with the SW density fixed and P_d < 4 nPa. The solid violet (orange) line indicates the regression () when P_d < 4 nPa.