Fig. 4: Dynamics of the observed MHD wave.

a–c Time-distance plots made from the AIA 193 Å base difference images along the three paths Slice 1, Slice 2, and Slice 3 shown in Fig. 1c. The black horizontal lines marked with p1–p10 in each panel indicate the positions used to extract the signal for analyzing wavefront amplitudes in Fig. 2. These positions are selected at an equal interval of 30 Mm and originate about 110 Mm from the starting point of the slices. The white horizontal lines labeled with white arrows mark the focal point and the far-side boundary of the coronal hole. In contrast, the oblique dotted yellow lines depict the linear fitting results for estimating the speeds of the wave. The speeds of the waves along different slices are listed in the corresponding panel. The error is estimated by making the fit ten times.