(a) Polar velocity in ecliptic plane from the SC and IH components during Carrington rotation 2121. The positions of STA, STB, and SOHO on 2012 March 7 are marked by pink, brown, and black dots, respectively. The black arrow represents the propagating direction of the associated CME. The solid lines represent the magnetic-field lines connecting each observer with the Sun. (b)–(d) Compression ratios of the reconstructed shock at 00:20:20 UT, 00:39:00 UT, and 00:54:00 UT are shown. The solid yellow, green, and purple lines are the magnetic-field lines connecting SOHO, STA, and STB to the SC component, respectively. The sphere represents the Sun. The coordinate system and axis scales are the same as those in Figure 2.