Snapshot from the EUHFORIA simulations showing the solar wind speed in the solar equatorial plane at March 15, 00:59 UT. Panel a depicts the scenario where CME5 is inserted with an increased initial density (details given in the main text), while panel b illustrates the circumsolar blast wave scenario. In both cases, a shock wave is visible arriving at STEREO A and Earth. The regions with speeds exceeding 1000 km s⁻¹ identify the two spheromak CMEs. Dashed lines represent the magnetic field lines passing through the various S/C, projected onto the solar equatorial plane. An accompanying movie is available online.