Manually scaled MUF(3000) time series for all ionosondes. The ionosonde closest to the eruption site is JR055 at 15,931 km. The values for the other ionosondes are shifted vertically by 2 MHz per 100 km additional distance from the eruption (see Table 1 for the precise distances). Points are connected by a line if values could be scaled from subsequent ionograms. Whenever for some reason, an ionogram is missing, or the MUF(3000) cannot be reliably scaled, the line is interrupted. The green and orange lines show the arrival times at various distances for the tropospheric acoustic wave, calculated respectively from the barometer data at Dourbes and Ebre. The dashed lines correspond to the waves travelling along the shortest great-circle sector, while the dotted lines correspond to the wave travelling along the longer sector. The grey bands indicate the expected arrival time for the TIDs assuming a delay of 40 min to 1 h from the ground level pressure wave and using the velocities calculated from the Dourbes pressure data for the latter.