Overview of the event. Panels a, b, and d: are AIA 171 Å, AIA 211 Å and LASCO/C2 snapshots, respectively. The field of view of panel c is marked by the white box in panel a. The incident and reflected wave trains are tracked with the two sectors indicated as S1 and S2, and the green line marks the location of the CH boundary in panel b. Panel e: solar soft X-ray recorded by the GOES in 0.5−4.0 Å (red) and 1.0−8.0 Å (blue). The green region marks the start and end time of the flare in NOAA AR 12473.